[MaxGhenis]

Fixes #2004
Fixes #1934. Main already keeps people on IS, JSA(IB), ESA(IR) or Universal Credit out of the pensioner scheme (#1944). This PR adds the issue's non-dependant deductions. The model lacks inputs for assessment-phase ESA(IR) and a working student's summer vacation.

Summary

The model now calculates Housing Benefit and national Council Tax Reduction non-dependant deductions under each scheme's own rules. We use legislation.gov.uk's 7 April 2025 text and each year's CTR amending instruments.

Housing Benefit (SI 2006/213 reg 74). SI 2006/214 reg 55 sets pension-age HB deductions.

Rule	Main	This PR
Banding, reg 74(2)	right=True puts £192.00 a week in the band below	Each band runs from "not less than" its lower edge
Remunerative work, reg 74(1)-(2), reg 6(1), (6)	For a non-worker the council deducts the lower of the flat amount and their band, so nothing for one with no banding income	For a non-worker, or anyone on IS, JSA(IB) or ESA(IR), the council deducts the reg 74(1)(b) amount whatever their income (£20.40 a week in 2026-27)
Couples, reg 74(3)-(4)	The council deducts for each member on their own income	The council makes one deduction for a couple, the higher, on the couple's joint income, and a separate one for any other adult in the family
Non-dependant exemptions, reg 74(7), (8), (10)	None	Full-time students; State Pension Credit recipients; under-25s on IS or income-based JSA, or entitled to Universal Credit that DWP calculates on no earned income
Claimant exemption, reg 74(6)	None	The council deducts nothing for anyone if the claimant or partner is blind or receives AA, the DLA care component, the PIP daily living component or AFIP

Council Tax Reduction. We model three national schemes:

• England, pension age: SI 2012/2885 Sch 1 para 8 and reg 10.
• Wales: WSI 2013/3029 Sch 1 para 3, Sch 6 para 5 and reg 10.
• Scotland: SSI 2012/319 reg 48 and reg 6; SSI 2012/303 reg 67, then SSI 2021/249 reg 90, reg 10 and reg 4.

Changes

• Scales. Main's national CTR used the Housing Benefit scale. We give each scheme its own weekly scale for 2013-14 to 2026-27 and cite the amending instrument for every year. In 2026-27:
  • England: £5.20 to £15.95, on £279/£485/£605.
  • Wales: £6.70 to £20.05, on the same bands.
  • Scotland: £5.55 to £16.55, on £286/£497/£614.
  • Pension-age and working-age scales match in Wales and in Scotland in every year. From 2027-28 the model uprates each scale's thresholds and amounts by gov.benefit_uprating_cpi.
• Banding, remunerative work and couples. As for HB. Councils treat recipients of IS, JSA(IB) or ESA(IR) as outside remunerative work under each scheme's reg 10(6) (SSI 2012/319 reg 6(6)).
  • Under Wales's working-age scheme, the council deducts for both members of a non-dependant couple whose own Universal Credit award assesses either of them (Sch 6 para 5(3): "other than where there is an award of universal credit"). Another member's award as a single claimant leaves the couple one deduction. Sch 1 para 3(3), for pension-age applicants, has no such words, so the council deducts both amounts only for a working-age applicant.
• Non-dependant exemptions, at any age (para 8(7)-(8) and equivalents): full-time students; non-dependants on IS, income-based JSA, income-related ESA or State Pension Credit; an adult for whom someone else has claimed child benefit (LGFA 1992 Sch 1 para 3 needs another person's entitlement, and SSAA 1992 s.1(1) makes entitlement depend on a claim); and entitlement to Universal Credit that DWP calculates on no earned income, from the year each scheme added it (England and Wales 2015-16, Scotland 2016-17).
  • From 1 April 2022, Scottish councils also exempt, under the working-age scheme, a non-dependant whose partner receives IS, income-based JSA or income-related ESA and who doesn't receive Universal Credit. SSI 2021/249 reg 90(8)(a) exempts a "qualifying income-related benefit claimant", which reg 4(1) defines as "an applicant who is, or who has a partner who is," on one of those benefits. Read literally, "applicant" would leave reg 90(8)(a) no case to apply to, so we read it for the non-dependant.
• Applicant exemption (para 8(6) and equivalents). We now apply council_tax_reduction_applicant_has_non_dep_exemption, which only the English local schemes read on main, to national CTR calculations.
• English working-age local schemes (Merton, Kingston, Newham, Westminster, Oxford) keep their own variables, unchanged.

New variables: housing_benefit_non_dep_deduction_exempt (Person), housing_benefit_non_dep_deductions_claimant_exempt (BenUnit), council_tax_reduction_non_dep_deduction_exempt (Person), uc_benefit_cap_welfare_benefits (BenUnit).

New parameters: HB income_related_benefit_age_limit (25); per CTR scheme, non_dep_deduction/{amount, exempt_universal_credit_without_earned_income}; Scotland working_age_exempt_partner_of_income_related_benefit_claimant (from 2022-04-01). HB age_threshold (18) now starts in 2006, when the 2006 Regulations took effect.

Universal Credit's cap. The new uc_benefit_cap_welfare_benefits holds the welfare benefits the Universal Credit cap counts: those in benefit_cap_welfare_benefits, for the same single person or couple, with Housing Benefit at nil (UC reg 80(2A)). uc_benefit_cap_reduction reads it where main read the combined total less housing_benefit_pre_benefit_cap. The Housing Benefit cap (HB reg 75C) keeps the combined total. A caller who supplies benefit_cap_welfare_benefits, a total that includes Housing Benefit, must also supply housing_benefit_pre_benefit_cap, which the new variable subtracts, or uc_benefit_cap_welfare_benefits itself, with a value for every benefit unit. Otherwise the new variable raises ValueError and names both inputs, whether or not any household has a non-dependant. A value a scenario stores with set_model_value supplies neither. No baseline formula on universal_credit's route then calculates Housing Benefit, so the deductions can read the award itself. uc_benefit_cap_reduction_after_floor keeps main's code. The baseline cap and award arrays match main (invariant 14).

Gross income

DWP instructs councils to count "earnings, and any other income" as a non-dependant's gross weekly income (HB guidance A5.542), to add savings interest to earnings (A5.570), and to take no business expenses off a self-employed person's total income (A5.551). Reg 74(9) and its equivalents disregard specified disability, compensation and trust payments.

• A person's own income comes from the programme's gross-income variable that Split total income into programme-specific concepts #2620 added (housing_benefit_non_dep_gross_income, council_tax_reduction_non_dep_gross_income): earnings, statutory sick, maternity and paternity pay, pensions, the taxable social security benefits, savings and dividend income, miscellaneous income, Maternity Allowance, IIDB, SDA, war widow's pension, and child and spousal maintenance. We add other investment income, ISA interest and ISA dividends, as main's local CTR schemes do. tax_free_savings_income counts ISA interest unless the inputs supply a total. The model holds self-employment and property profits rather than the receipts A5.551 describes, so we count each profit and treat a loss as nil.
• A claimant or partner of the non-dependant's family: the council bands them on the couple's two incomes plus the family's awards: child and working tax credits, child benefit, Income Support, the couple's income-based JSA and income-related ESA (claimant_or_partner_jsa_income, claimant_or_partner_esa_income), Pension Credit, and Universal Credit where the award assesses either of them. It bands anyone else in the family on their own income, plus the Universal Credit where is_uc_claimant makes them its claimant instead.
• Universal Credit. The council counts the family's award after the cap and before debt deductions, so the model reads universal_credit, plus uc_deductions where the award is positive. DWP awards the maximum amount less the amounts for income (Welfare Reform Act 2012 s.8(1)). DWP then takes advances (SI 2013/383 reg 10), overpayments (SI 2013/384 regs 10-11) and third-party payments (SI 2013/380 Sch 6 para 2(1)) from the sum payable, so those deductions stay the family's income.
  • A stored award, a stored or replaced cap reduction and a reform of universal_credit's formula reach the deduction through universal_credit itself.
  • Parliament lists Maternity Allowance as a welfare benefit (Welfare Reform Act 2012 s.96(10)(i)). uc_benefit_cap_welfare_benefits reads it through CLAIMANT_OR_PARTNER_BENEFITS, so DWP's cut reaches the award the council counts. For a non-dependant family with £20,000 of Universal Credit before a £14,753 cap and £5,000 of Maternity Allowance, DWP pays £9,753 of Universal Credit, and the council counts that award.
  • No baseline formula on Universal Credit's route calculates Housing Benefit, so the deduction reads universal_credit without a cycle in any mix of households, and housing_benefit_non_dep_deductions needs no early return. A supplied combined total comes with a supplied housing_benefit_pre_benefit_cap or uc_benefit_cap_welfare_benefits for every benefit unit (invariant 15). A reform can add a read of calculated Housing Benefit to that route; the engine then raises CycleError in the deduction, as it does in universal_credit.
  • A reform that replaces or neutralizes benefit_cap_welfare_benefits changes the Housing Benefit cap alone. To change the benefits the Universal Credit cap counts, a reform replaces uc_benefit_cap_welfare_benefits. A reform that neutralizes housing_benefit_pre_benefit_cap drops a supplied value, so a caller who supplies the total under it supplies uc_benefit_cap_welfare_benefits; the ValueError message says so.

Inputs and choices

• On a benefit. The exemptions and the remunerative-work test read Count only the claimant's and partner's legacy awards in means tests and passports #2027's is_on_income_support, is_on_income_based_jsa, is_on_income_related_esa and is_on_pension_credit, which ask whether DWP pays the award to that person (HB reg 2(1), (3), (3A)). Universal Credit counts for each claimant its award assesses (is_uc_assessed_claimant, the claimant and partner unless is_uc_claimant names others). For entitlement we read the award before the cap (universal_credit_pre_benefit_cap > 0): UC reg 80(2) uses "the amount to which the claimant is entitled before any reduction under regulation 81".
• Full-time student: current_education != NOT_IN_EDUCATION or in_HE, the helper the local schemes use. With no input, the model gives an 18- or 19-year-old tertiary education, so it counts them as students.
• Claimant or partner: is_claimant_or_partner (Replace generic child and adult flags with each programme's legal definitions #1896), the benefit unit's claimant and at most one partner (SSCBA s.137).
• "Earned income" in the Universal Credit limb. HB reg 74(11) and the CTR provisions adopt UC reg 52's definition of earned income. We read uc_individual_earned_income, so UC's deductions, company attribution, trading losses and conditional minimum income floor reach the exemption. DWP takes allowable employment expenses, tax, National Insurance and relievable pension contributions off earnings (UC reg 55(3), (5)). It adds trades' profits and losses together and attributes a company's income to its owner (reg 57(2), reg 77(3)(b)), and it applies the minimum income floor only where reg 62 does, a couple's floor included. The limb asks whether "the award is calculated on the basis that the non-dependant does not have any earned income", and DWP calculates a joint award on combined earnings under reg 22(1)(b). We test the non-dependant's own earned income; we found no DWP guidance on joint claims.

Not modelled

• Pension-age HB's 26-week deferral of an increase in a deduction (SI 2006/214 reg 59(10)-(13)), and the CTR applicant exemption's protection while DWP suspends AA, DLA or PIP during a hospital stay.
• HB: a working full-time student's summer vacation (reg 74(7)(d)). No input separates assessment-phase income-related ESA from the work-related activity group, so we withhold the reg 74(8)(a) exemption from every under-25 on ESA(IR).
• Wales: Welsh councils deduct for ESA(IR) recipients in the work-related activity group; we exempt every recipient. esa_includes_support_component marks the support group only.
• CTR: people whom the council tax discount rules disregard (LGFA 1992 Sch 1), other than students and the para 3 adults. is_apprentice has no £195 earnings cap, so we don't read it.
• All schemes: youth training allowances, a normal home elsewhere, long hospital stays, prison and armed forces operations, and the benefit-week and leave rules of reg 6 (annual hours stand in for them).
• Gross income: student support; statutory adoption, shared parental, parental bereavement and neonatal care pay (no inputs).
• Joint-claim JSA couples (HB reg 2(3)(c)): with no joint-claim input, the model counts only the payee as receiving it.
• Scottish disability assistance for the claimant exemption has no separate input.

How this composes with main

• Housing Benefit (housing_benefit_non_dep_deductions). For each family we sum each other family's amount (one per couple, the higher, plus one for each other member) over the non-dependants of the household head (Give sharers, boarders and lodgers their own rent, tenure and LHA category #2006). We treat a family that bears any share of the rent as a joint occupier, not a non-dependant (reg 3(2)(d)), even at nil rent. We then multiply the total by the family's share_of_household_rent (reg 74(5)) and zero it under the family's own claimant exemption.
• Council Tax Reduction (council_tax_reduction_non_dep_deductions). Each applicant family takes its deductions under its own scheme (council_tax_reduction_pensioner, Assess each Council Tax Reduction claim under its own family's scheme and exemption #2015). The person-level variables report the scheme of the household head's family, which Give Council Tax Reduction to the household head's family, not the oldest adult's #2009 makes the applicant; for a jointly liable applicant on the other scheme, _national_non_dependants.py recomputes the deductions under that scheme. We multiply the total by council_tax_reduction_joint_liability_share (para 8(5)) and zero it under the family's own council_tax_reduction_applicant_has_non_dep_exemption.
• Split total income into programme-specific concepts #2620's work gate becomes the full rule: inclusive band edges, the flat amount for every non-worker who isn't exempt, and the exemptions. Its remunerative-work-hours parameters, including the Northern Ireland reference, stay as main has them.

Invariants

The property tests check these over generated populations (10 examples each, with explicit cases for rare combinations), the exhaustive edge test checks invariant 7, the fixture comparison invariant 8, test_rent_of_sharers_boarders_and_lodgers_properties.py invariant 10, differential runs invariant 14, and test_non_dependant_cycle_contracts.py and test_non_dependant_population_consistent_total.py invariant 15:

1. The council deducts nothing for an exempt non-dependant, for HB and CTR.
2. For an eligible, non-exempt non-dependant the council deducts between the scale's lowest and highest amounts. The council makes no national CTR deduction in English working-age households.
3. For a non-dependant working under 16 hours, or (for HB) on IS, JSA(IB) or ESA(IR), the council deducts the lowest amount whatever their income.
4. The council deducts nothing when the claimant or applicant has an exemption.
5. A family's deductions equal the sum, over the other families in the household, of each family's higher couple amount (both for a Welsh working-age applicant's non-dependant couple whose own Universal Credit award assesses either member) plus each other member's, times the family's share of the rent (HB) or council tax liability (CTR). The generated populations vary is_uc_claimant, so another member's award as a single claimant appears.
6. Raising a non-dependant's income never lowers any deduction.
7. In every year 2015-2030 (2019-2030 for HB), the council deducts a band's amount for an income at its lower edge, and the band below's amount for the next lower representable income.
8. Every CTR parameter value equals the enacted sums in tests/fixtures/council_tax_reduction_non_dependant_deductions.yaml.
9. The exemption flags equal a reading of the provisions that the test computes from the inputs, with Universal Credit's earned income from invariant 13.
10. HB deductions over the families liable for a household's rent equal the pooled amount (one per couple, the higher, with sharers never in the pool) times the share that families without an exempt claimant bear, and never exceed the sum of individual deductions.
11. For a non-dependant in remunerative work who is neither exempt nor on IS, JSA(IB) or ESA(IR), the council deducts the amount of the band containing the gross income that the test computes from the inputs.
12. Universal Credit's cap counts the Housing Benefit cap's welfare benefits other than Housing Benefit. No baseline formula on Universal Credit's route calculates Housing Benefit: its traced calculation reads no Housing Benefit variable but the reported award, and, where the inputs supply the combined total, the supplied housing_benefit_pre_benefit_cap. A reform can add a read of calculated Housing Benefit, and its cycle raises CycleError. The Universal Credit in a non-dependant family's gross income equals universal_credit plus uc_deductions. That sum equals the award before the cap less the cap reduction applied, under current law and under an 85% protected minimum floor, and the floor never lowers an award. Under a reform that scales universal_credit, each household's HB and CTR deductions equal those of the same household with the reformed award supplied. The HB deduction equals the band of wages plus that award, so it moves when the award crosses a band.
13. For each claimant the award assesses, the Universal Credit exemption agrees with uc_individual_earned_income across employment expenses, trading losses, company income, pension contributions and single and couple floors, and with the inputs wherever they settle it without the tax and National Insurance calculation.
14. At 02cc0896f, under current law and under the 85% floor, main and that head gave bit-identical uc_benefit_cap_reduction, uc_benefit_cap_reduction_after_floor, uc_deductions and universal_credit arrays for 60 families on Universal Credit, and main's cap formulas and that head's gave identical arrays over 4,096 rows of inputs, with and without a supplied cap reduction and a protected floor. At 95fbf3014 the same 60 families give arrays bit-identical to 02cc0896f's. Where a family supplies Housing Benefit alongside Universal Credit, which the model's Housing Benefit eligibility rules out when it calculates both, the basket differs from main's combined total less Housing Benefit by at most £0.004, one float32 step.
15. Inputs that supply benefit_cap_welfare_benefits also supply housing_benefit_pre_benefit_cap or uc_benefit_cap_welfare_benefits; otherwise the model raises ValueError when it calculates Universal Credit's cap, with or without a non-dependant in the population. A value stored with set_model_value supplies neither, and a reform that gives the combined total a formula leaves Universal Credit's basket on its own sum. When the inputs give each benefit unit its own values, each household's Universal Credit, Housing Benefit and HB non-dependant deductions equal its results alone, for any mix of independent households and whichever result the first request asks for. A situation that sets either input for some benefit units stores nil for the rest.

Tests

• YAML (hand-worked expectations from the law):

  • HB band edges in and out of remunerative work (2026-27), 2025-26 cases in four of the six bands, couples, a dependent child's income, each exemption and its age boundary, each claimant exemption (a partner's PIP included), and aggregation, where a family with a 0.5% share of the rent is a joint occupier.
  • CTR band edges for each scheme (2026-27, with 2025-26 checks), every exemption at age 40, the UC-limb start dates, couples including the Welsh UC rule, the applicant exemption, and jointly liable applicants under different schemes.
  • The Universal Credit exemption follows Universal Credit's earned income. Wages cancelled by allowable expenses, or a profit cancelled by a trading loss, leave none, so the council deducts nothing. A company's income attributed to its owner counts, so the councils deduct £1,060.80 (HB) and £348.40 (Welsh CTR) a year. A partner whose earnings meet the couple threshold keeps the minimum income floor off the other member, so the Welsh deduction for the couple comes to £348.40, not £696.80.
  • In Wales, a third adult's own Universal Credit leaves the couple one deduction: £694.20 a year, and £521.30 for each of two jointly liable applicants on different schemes.
  • The gross-income variables count other investment income, ISA interest and ISA dividends (£9,000 of wages, £20,000 of exempt interest and £30,000 of ISA dividends give £59,000), and treat a self-employment or property loss as nil.
  • A family's Universal Credit counts in the income of the claimant it assesses, and another adult's own income-related ESA stays out of the couple's income: £2,121.60 in each case, where counting the award in the parents' income would give £4,407.00.
  • A non-dependant family's Universal Credit counts after the cap: DWP counts the partner's £6,000 of Maternity Allowance and cuts the award from £14,000 to £10,890.20, so the couple's £600.38 a week falls in the £485 bands, £6,232.20 HB and £691.60 CTR.
  • Universal Credit's cap leaves out Housing Benefit the family receives. With £15,000 of Universal Credit, £5,000 of child benefit and £10,000 of Housing Benefit, the Housing Benefit cap counts £30,000 and Universal Credit's £20,000, so the award comes to £9,753. A supplied £26,000 total with £6,000 of Housing Benefit gives a £14,753 award.
  • End to end: a 40-year-old claimant paying £6,000 rent with a zero-income full-time student gets £6,000 of HB; a Guarantee Credit pensioner whose son earns £30,000 at 37.5 hours has a £691.60 deduction and £1,308.40 of CTR (National council tax reduction: non-dependant deductions use Housing Benefit amounts and skip exemptions; pensioner gate ignores benefit exclusions #1934's example).

• Main's tests that change. Each move follows from the law:

  • household_benefits_individual_non_dep_deduction.yaml:
    • "Other investment income does not band a non-worker": £0 becomes reg 74(1)(b)'s £19.65 × 52 = £1,021.80.
    • "Other investment income does not move a worker's band" becomes "A worker's band counts their investment income": £739.02 a week falls in the top band, £126.65 × 52, where main banded the earnings alone at £45.15.
    • The 2018 case keeps HB at £793. Its CTR half moves to Wales's own scale, £4.35 a week from 1 April 2018 (WSI 2018/14), £226.20; England has no national scheme for a working-age household.
    • Every single-person case now holds the family's awards at zero. The council bands a claimant or partner of the non-dependant's family on the couple's income plus those awards (reg 74(4)), so without them the case's stated income wouldn't be its gross income.
  • housing_benefit_non_dep_remunerative_work.yaml (Split total income into programme-specific concepts #2620): for the nil-income non-worker the council deducts £20.40 × 52 = £1,060.80 (reg 74(1)(b)), not £0; the under-25 on Income Support now reaches £0 through the reg 74(8)(a) exemption, and the case computes eligibility instead of taking it as an input.
  • council_tax_reduction_non_dep_remunerative_work.yaml (Split total income into programme-specific concepts #2620), 37 cases: each scheme's 2026-27 scale replaces the HB scale. For non-workers the councils deduct £270.40 (England), £288.60 (Scotland) or £348.40 (Wales) a year, and for £403.85 a week in work £551.20, £569.40 or £694.20. For a recipient of IS, JSA(IB) or ESA(IR) they deduct nothing (para 8(8)(a)), and for the nil-income non-worker England's £270.40. Each English case with a 30-year-old non-dependant now gives the household a separate 70-year-old applicant, and the model works out each family's scheme.
  • council_tax_reduction_non_dep_gross_income.yaml (Split total income into programme-specific concepts #2620), 15 cases: £183.08 a week falls below every scheme's first band edge, so each scheme deducts its 2025-26 lowest amount (England £260, Scotland £278.20, Wales £325 a year) and the reduction comes to £4,000 less that.
  • test_non_dependant_spousal_maintenance.py: the national CTR comparison moves to Wales, whose scheme covers working-age applicants: [£348.40, £348.40, £694.20, £348.40].
  • housing_benefit_non_dep_deductions.yaml: for the non-worker with investment income the council deducts £19.65 × 52 = £1,021.80, where main's right=True gave £0.
  • council_tax_reduction_individual_non_dep_deduction.yaml, on England's 2025-26 pensioner scale (SI 2025/39): for a non-worker with £556 a week of investment income the council deducts £5.00 × 52 = £260, and a worker's band counts it, £15.35 × 52 = £798.20.
  • council_tax_reduction_pension_credit.yaml: for the son with no hours the council deducts England's £5.20 a week, so CTR is £1,729.60. claimant_family_scheme.yaml: for the 40-year-old adult child it deducts £5.20 × 52 = £270.40, so CTR is £1,529.60.
  • housing_benefit_individual_non_dep_deduction_eligible.yaml: the 18-year-old "Eligible" case sets current_education and would_claim_uc: false; otherwise the age default makes them a student, and an income-free 18-year-old has Universal Credit without earnings.
  • test_rent_of_sharers_boarders_and_lodgers_properties.py: the HB pool counts one deduction per couple, the higher, and only families without an exempt claimant bear it (invariant 10).
  • benefit_cap_by_scheme.yaml, "UC reg 81(2) - no reduction where the childcare costs element exceeds the excess": the case supplies the combined total, so it now supplies the £0 of Housing Benefit the model calculates for it, and its outputs don't change. The other eight YAML cases that supply the total already supply housing_benefit_pre_benefit_cap. Before this change only one Python test supplied the total, the one in test_non_dependant_deduction_properties.py that this PR rewrites.
  • pension_age_severe_disability_conditions.yaml, claimant_household_head.yaml, housing_benefit_non_dep_gross_income.yaml and test_housing_benefit_non_dep_history.py change only in comments, apart from the new ISA case in the gross-income file.

• test_non_dependant_deduction_properties.py: Hypothesis populations for invariants 1-6, 9 and 11, which vary is_uc_claimant, with explicit examples for the rare Welsh-couple and under-25 cases; the exhaustive edge check (7); the fixture comparison (8); and the earned-income comparison (13). For invariant 12, one property compares the basket and the award under current law and an 85% floor with debt deduction rates; its explicit example takes £720.25 of debt and no cap reduction, so the award counts £20,000. Another scales the award by a reform, and its explicit example moves a non-dependant from the 348 band to the 266 band. A third traces Universal Credit, which reads no calculated Housing Benefit, and checks that a supplied total without Housing Benefit raises ValueError. The invariant 12 tests build core simulations on one tax-benefit system for the module.

• test_non_dependant_cycle_contracts.py (invariant 15) uses two independent households: a single Universal Credit claimant with £20,000 before a £14,753 cap and no rent, and a 70-year-old paying £6,000 rent with a non-dependant who earns £9,000 at 20 hours and claims no Universal Credit. For the second's non-dependant, the council deducts £19.65 × 52 = £1,021.80 (HB regs 70 and 74(2)(a), 2025-26), leaving £4,978.20 of Housing Benefit.

  • With the combined total and Universal Credit's basket supplied, the population gives Universal Credit of [£14,753, £0, £0] and Housing Benefit of [£0, £4,978.20, £0], each household's results alone, whether the first request asks for Universal Credit, Housing Benefit or the family deduction.
  • With Housing Benefit supplied instead, the basket counts the total less that Housing Benefit: £26,000 less £6,000 leaves £20,000, and the award comes to £14,753.
  • A supplied total with neither raises ValueError, with or without the non-dependant. set_model_value supplies neither input, and a reform that gives the total a formula leaves Universal Credit's basket on its own sum.
  • For any mix of up to three independent households, some with a non-dependant on Universal Credit, and Universal Credit's basket supplied, a Hypothesis property checks that each household's Universal Credit, Housing Benefit and deductions equal its results alone.
  • Reforms that add calculated Housing Benefit to Universal Credit's basket or to its award before the cap raise CycleError. With nothing supplied, a traced run shows Universal Credit reading only reported Housing Benefit, and the national and five local CTR schemes then read Universal Credit.

• test_non_dependant_population_consistent_total.py takes each household's combined total and Housing Benefit from its own simulation with nothing supplied (£20,000 and £0; £4,978.20 and £4,978.20). Supplied together for the mixed population, they give each household its results alone for each first request, and the totals without the Housing Benefit raise ValueError.

• code_health/test_benefit_cap_lists_unique.py checks that each name occurs once in the lists the two caps and a non-dependant family's income add up.

• Mutation testing. At 97f792542 the tests killed the mutants of the earned-income limb, the Welsh couple rule, either exemption's earned-income test, the ISA income, the joint-occupier share and the partner's PIP. At 86e86d3db they killed every other mutant of the rules except one that removes CTR's reg 10(6) work exclusion, which changes no result, because each scheme's para (8)(a) exemption already gives such a non-dependant no deduction. At 02cc0896f, the tests killed nine of ten mutants of the award and the cap's basket:

  • the award dropping its debt deductions, rebuilding itself from the cap variables in place of universal_credit, or counting Universal Credit before the cap;
  • uc_benefit_cap_reduction reading the combined total with Housing Benefit; a supplied combined total never reaching the cap, or keeping its Housing Benefit; the basket leaving out income-based JSA and income-related ESA;
  • housing_benefit_non_dep_deductions reading income with no non-dependant, or returning nil for every household.

  The survivor adds debt deductions to a nil award. It changes no result under current law, where a positive deduction always leaves at least a penny of award. The basket leaving out child benefit and the cap ignoring the childcare costs element also failed their tests at 02cc0896f. This head deletes the early return that the no-non-dependant mutant changed.

  We also ran two mutants of the supplied-total contract. Restoring the calculated read, so that the basket subtracts housing_benefit_pre_benefit_cap from a supplied total whether or not the inputs supply it, makes test_a_supplied_total_alone_raises[mixed] and [single] raise CycleError instead of ValueError, and test_model_values_supply_neither_input stops raising. Dropping the ValueError, so that a supplied total without Housing Benefit counts in full, makes all three stop raising.

• Differential against main. In 20 households with 40 people in five English councils (Merton, Kingston, Newham, Westminster and Oxford), each non-dependant earns £9,000 and has nothing else, £20,000 of other investment income, a £5,000 self-employment loss or a £5,000 property loss. At 86e86d3db, main 2da212abc and the head gave identical arrays for all five local schemes' reductions, individual and family non-dependant deductions, and the shared eligibility, applicant-exemption, pensioner and joint-liability flags: 19 of 21 arrays. The two national gross-income arrays differed in the 15 investment and loss cases: £9,000 becomes £29,000 with investment income, and £4,000 becomes £9,000 with a loss.

• Runs, locally with no survey data, each file alone under a 4 GB memory cap (2 GB for mutants), at 95fbf3014 unless stated. 2667976b8 then adds only a module-scoped fixture that clears scaled_award_system's cache.

  • YAML: gov/dwp/benefit_cap/ 118 passed, the HB non-dependant directory 139, gov/local_authorities/council_tax_reduction/ 376, and benefit_cap_by_scheme.yaml 22 at 2667976b8.
  • test_non_dependant_cycle_contracts.py 14 passed, test_non_dependant_population_consistent_total.py 5, test_non_dependant_deduction_properties.py 10 (also at 2667976b8), test_uc_deductions.py 24, test_benefit_cap_uc_and_hb_properties.py 1, the sharers properties 6 and the LHA scheme-split properties 7.
  • code_health/ without test_changelog_fragments.py: 2,999 passed and 2 failed. test_pytest_default_collection_confirms_function_and_class_names fails only when PYTEST_ADDOPTS carries -n 0 into its nested pytest, and passes without it. test_every_test_module_cache_is_released found scaled_award_system's module-level cache, which 2667976b8 releases; at 2667976b8 that file reports 5 passed. test_changelog_fragments.py, run on its own with towncrier installed, reports 103 passed.
  • The 60-family cap differential gives bit-identical uc_benefit_cap_reduction, uc_benefit_cap_reduction_after_floor, uc_deductions and universal_credit arrays at 95fbf3014 and 02cc0896f, under current law and under the 85% floor.
  • ruff format --check, ruff check, ruff check --select F811,F821 and git diff --check against main report nothing.
  • At 4ec0693f7, whose two commits after 2667976b8 change only documentation strings, comments, the changelog and the ValueError message's text (no test asserts the changed wording; with every string literal blanked, each changed Python file parses to the same tree): test_non_dependant_cycle_contracts.py 14 passed, test_non_dependant_population_consistent_total.py 5 and gov/dwp/benefit_cap/ YAML 118 at c2c55086e; test_non_dependant_deduction_properties.py 10, code_health/test_test_module_caches_released.py 5 and test_parameter_descriptions.py 24 at 4ec0693f7; code_health/ with towncrier installed 3,104 passed at c2c55086e; ruff format --check, ruff check, ruff check --select F811,F821 and git diff --check report nothing at 4ec0693f7.

Impact (Enhanced FRS 2024-25, certified uk-data 1.58.1)

CI's aggregate impact job (run 42404565262) compared main e0502003d with 04af7282b, its merge of this head into that main. It ran each fiscal year as a full microsimulation on both sides, on the certified dataset (sha256 056e80fd8e91), and broke no check. It flagged two moves, both in 2025-26: decile 5's mean household net income rises by £96 and decile 4's falls by £70. The job sorts each side's households into deciles by that side's incomes. In the base run's deciles, we estimate that households gain £2 on average in decile 4 and £3 in decile 5.

Change	2025-26	2026-27	2027-28	2028-29	2029-30	2030-31	2031-32
Housing Benefit (£m)	+16.1	+11.2	+11.6	+12.0	+12.3	+13.0	+12.5
Council Tax Reduction (£m)	+9.8	+10.4	+10.9	+11.5	+12.0	+12.5	+13.1
Household net income (£m) †	+25.9	+21.6	+22.5	+23.5	+24.3	+25.5	+25.6
Housing Benefit caseload	+238	+30	+30	+30	+31	+31	+31
CTR caseload (k)	+6.9	+7.1	+7.1	+7.2	+6.8	+6.8	+7.1

† Fewer than 10 records receive Disabled Students' Allowance in each year, so the job withholds it and leaves it out of household net income and the two flagged decile moves.

Tax receipts and population don't change in any year. We estimate that absolute poverty after housing costs falls by 2.2k to 3.3k people a year, and absolute poverty before housing costs rises by 47 to 1.3k. We also estimate that relative poverty after housing costs falls in six years, by up to 5.2k (2030-31), and rises by 69 in 2025-26. Some households lose, since councils now deduct a flat amount for non-workers and count more kinds of income in the bands.

Merge with main

0198ce4c98b3ec37f8bf6d11a5c125c8cc8b7865 merges main at 5c7744144 into fde435bd3 with a merge commit. Git stopped on two files, and the merge keeps both sides in each:

• docs/book/programs/gov/dwp/housing-benefit.ipynb, step 3 ("Means test"). This PR adds the sentences on reg 74's bands, couples and exemptions after the reg 70 sentence. main appends sentences on applicable income: income tax and National Insurance come off earnings, pensions and benefits, regulation 46(4) and the pension-age Schedule 5 paragraph 22 treat income from capital as capital, and the rent for letting part of the home counts less £20 a week per occupier. The merged sentence runs reg 70, this PR's sentences, the taper and Northern Ireland sentences, then main's.
• policyengine_uk/tests/shard_durations.toml: this PR's four test_band_edges_are_inclusive timings and main's seven test_person_isa_capital.py timings with their comment, at the same place.

Git merged every other file, uc_benefit_cap_reduction.py, supplied_inputs.py, programs.yaml and council_tax_reduction_pension_credit.yaml among them, without a conflict. At the merge, this PR's 20 YAML test files report 339 passed, and its seven Python test files (test_benefit_cap_lists_unique.py, test_housing_benefit_non_dep_history.py, test_non_dependant_cycle_contracts.py, test_non_dependant_deduction_properties.py, test_non_dependant_population_consistent_total.py, test_non_dependant_spousal_maintenance.py and test_rent_of_sharers_boarders_and_lodgers_properties.py) report 48 passed, so main moved none of this PR's results. main did move one test of its own: benefit_cap_reduction_applied.yaml, new on main, supplies benefit_cap_welfare_benefits alone in seven cases, so at the merge each raised this PR's ValueError (invariant 15) and gov/dwp YAML reported 7 failed and 961 passed. 6900b88b7 supplies the nil Housing Benefit the model calculates for each case, which has no rent, as this PR did for benefit_cap_by_scheme.yaml; the outputs don't change, and the file reports 8 passed. main's #2815 adds uc_receives_attendance_allowance, which this PR doesn't read: the HB and CTR claimant exemptions follow their own regulations and count armed forces independence payment separately.

At 6900b88b7006fbc96690839ff297f16003459c23, locally with no survey data, each run under -n 4:

• policyengine-core test on finance/benefit/family 1,808 passed, gov/dwp 968 passed and gov/local_authorities/council_tax_reduction 391 passed, none failing;
• test_non_dependant_deduction_properties.py 10, test_council_tax_reduction_claimant_properties.py 3, test_household_head_agreement_properties.py 3 and test_uc_afip_housing_contribution_properties.py 3 passed; the other files that read uc_non_dep_deductions, uc_receives_attendance_allowance or uc_is_ineligible_partner: test_benefit_cap_lha_scheme_split_properties.py 7, test_rent_of_sharers_boarders_and_lodgers_properties.py 6, test_uc_legacy_closure_properties.py 4, test_uc_non_dep_pension_credit.py 3, test_uc_receiving_education_properties.py 5, test_uc_single_claim_properties.py 8 and test_uc_work_related_groups_properties.py 14 passed; policyengine_uk/tests/code_health 3,168 passed;
• uvx ruff@0.17.2 format --check ., ruff check . and ruff check --select F811,F821 policyengine_uk report nothing; git diff --check over this branch's new commits reports nothing; git merge-tree --write-tree --name-only HEAD origin/main against main at 5c7744144 reports no conflict; .github/check_fix_pr.py passes on this title and body.

7e239f148048fb4735154b2b167185659d8aaa35 merges main at 47a2817e2 into 6900b88b7, which brings in #2811. Git stopped on one file, the documentation of benefit_cap_welfare_benefits. The merge keeps this PR's sentences on the two baskets and the supplied total, and #2811's sentences on Maternity Allowance and the other welfare benefits. 4f3962360f4e9f042ea705859ffda507ae9c4221 moves the case "A non-dependant family's Universal Credit counts after the benefit cap" to the figures its comment worked out: universal_credit [£0, £10,890.20], housing_benefit_non_dep_deductions [£6,232.20, £0] and council_tax_reduction_non_dep_deductions [£691.60, £0]. The local runs above read 6900b88b7; CI tests this head.

ce2aef8c6f393e87d973cfa069ba09cb5d4764a9 merges main at fed9bcabe into 4f3962360, which brings in #2813, #2819 and #2826. Git stopped on one file, the comment above CLAIMANT_OR_PARTNER_BENEFITS in benefit_cap_welfare_benefits.py. The merge keeps this PR's sentence on uc_benefit_cap_welfare_benefits and #2813's sentences on a family receiving both awards. #2813's case in esa_income_abolition.yaml reads benefit_cap_welfare_benefits and uc_benefit_cap_reduction as outputs, and this PR's basket gives its £2,442.20 reduction: £24,462.20 of benefits against the £22,020 cap.

ae4721f2457622593bd1b0e64ad2980f6e83dfe1 sets would_claim_uc_at_legacy_closure: false on two cases in non_dependant_deduction_review_cases.yaml. #2813's esa_income_abolition_reached moves a couple reporting income-related ESA to Universal Credit in 2026, and the award joins the band income: in the case "Income-related ESA is payable to the recipient, not the working partner", the partner moves from the £192 band to the £279 band, and the deductions rise from £2,436.20 to £3,346.20 for Housing Benefit and from £270.40 to £551.20 for Council Tax Reduction. These two cases test how income-related ESA counts in the band, so the couples stay on it. Their figures don't change.

fe69a8caaf568ef296a5fd347e9e4e3fd8586e07 merges main at e0502003d into ae4721f24, which brings in #1966 and #2002. Git stopped on two files, and the merge keeps both sides in each:

• housing_benefit_individual_non_dep_deduction_eligible.py: Model rent from boarders, lodgers and sub-tenants for the householder #2002's exclusion of a boarder or lodger and their partner (pays_rent_to_householder, reg 3(2)(e)(i)) and this PR's exemptions (housing_benefit_non_dep_deduction_exempt), with references to reg 3, reg 74 and HB (SPC) reg 55.
• programs.yaml: Give Scotland and Wales working-age CTR their own rules #1966's Council Tax Reduction notes, plus this PR's non-dependant deductions and exemptions for each scheme.

Both of this PR's Council Tax Reduction deduction paths read council_tax_reduction_individual_non_dep_deduction_eligible, which keeps #2002's exclusion. At the merge, CI's YAML job failed one of 6,220 cases. #2002's case "A lodger's non-paying adult son is the householder's non-dependant for Universal Credit and CTR" expected the Housing Benefit scale, which CTR used before this PR. cc94e715b0325650e90a90a780c442788d821090 moves the case to Scotland's own scale (SSI 2021/249 reg 90(2)(b)). The son earns £300 a week, in the band from £286 to £497, so the council deducts £10.95 a week, £569.40 a year, in place of £3,346.20.

52fbb2400ee24f9f1966ca9080622306f4695adc puts main's shard_durations.toml back, without this PR's seven timings for test_non_dependant_deduction_properties.py. conftest.py deals the tests that table lists out longest first, each to the least loaded shard. The seven timings moved most of the shorter tests, and Python shard 7 of 7 took three more tests from tests/microsimulation/. CI logs each runner's memory once a minute, and with main's table shard 7's largest sample already reads 15,468 MiB used and 472 MiB available (run 42393088220). With this PR's table, one worker ran the shard's microsimulation tests back to back from the start (run 42402370483 here, run 42402482489 on #2010). In both runs the log read over 15,400 MiB used and about 500 MiB available in the first 77 seconds, and the runner shut down with 13% of the tests run. The seven property tests now take their shards from the hash, and all seven Python shards ran to the end at this head (run 42404565211).

Shard 5 fails one test, main's #2002 property test_a_non_paying_adult_counts_the_same_in_or_out_of_the_payers_unit (job). The property moves a non-paying adult from the payer's benefit unit into their own and expects the household head's deductions not to change. Under this PR, councils make no Council Tax Reduction deduction for an adult whose own family claims Universal Credit that DWP calculates on no earned income. The model reads that award only for a family's claimant and partner. Hypothesis found two 83-year-olds renting privately in the North West in 2026, with a boarder aged 27 and a non-paying adult aged 57 who earns nothing. With the adult in the boarder's unit, the council deducts £5.20 a week under England's pension-age scheme, £270.40 a year. In a unit of their own, the adult claims Universal Credit, and the council deducts nothing.

#2010's 7ff98b0b0 sets would_claim_uc to false for the adult's own family in that comparison, so the adult claims no Universal Credit in either unit. #2010 passes the property and every other check at 4bb3813f4, and this PR would need the same change to land alone.

Merge order and overlaps

• On main, and composed here: Replace generic child and adult flags with each programme's legal definitions #1896, Set DWP benefit rates to the announced amounts, not CPI projections #1925, Give Scotland and Wales working-age CTR their own rules #1966, Model rent from boarders, lodgers and sub-tenants for the householder #2002, Give sharers, boarders and lodgers their own rent, tenure and LHA category #2006, Give Council Tax Reduction to the household head's family, not the oldest adult's #2009, Assess each Council Tax Reduction claim under its own family's scheme and exemption #2015, Count only the claimant's and partner's legacy awards in means tests and passports #2027, Means-test the Council Tax Reduction applicant and partner, not the benefit unit's claimant #2078, Give Universal Credit and Housing Benefit their own benefit cap and LHA shared-accommodation rules #2089, Split total income into programme-specific concepts #2620, Report the benefit cap reduction actually applied to Universal Credit #2647, Apply the Universal Credit education condition #2806, Count Maternity Allowance in the benefit cap #2811.
• Charge non-dependant deductions within the claimant's benefit unit #2017 (in-unit non-dependants) stacks on this branch, and its head ae2be5fbe contains this PR's ae4721f24 by merge. Give benefit-unit members aged 16 or over a bedroom under LHA rules #2010's head 4bb3813f4 contains this head and Charge non-dependant deductions within the claimant's benefit unit #2017's by merge, so landing Give benefit-unit members aged 16 or over a bedroom under LHA rules #2010 lands this PR and Charge non-dependant deductions within the claimant's benefit unit #2017. Charge in-unit non-dependants in the local Council Tax Reduction schemes, and exclude a lodger personally only outside the head's family #2077 stacks on Charge non-dependant deductions within the claimant's benefit unit #2017 and conflicts with Charge non-dependant deductions within the claimant's benefit unit #2017's head in one file, council_tax_reduction_prescribed_benefits.yaml.
• Apply each scheme's own non-dependant test to the LHA shared accommodation rate #2030 and Count a non-dependant shared by joint tenants in each tenant's Housing Benefit size criteria #2035 conflict with this head in 22 and 16 files; each owner resolves them when restacking.
• Give Scotland and Wales working-age CTR their own rules #1966's working-age route for Scotland and Wales subtracts council_tax_reduction_non_dep_deductions in simulated_council_tax_reduction_benunit, as the shared route does, so Scottish and Welsh working-age awards take these deductions.
• supplied_inputs.py: this head registers benefit_cap_welfare_benefits and housing_benefit_pre_benefit_cap in SUPPLIED_INPUT_VARIABLES, since the new basket asks whether the inputs supply them. Git merges that file cleanly with Value means-tested capital less 10% sale expenses and secured debt #1969, Give UK simulations a working subsample #2265, Count only supplied inputs that are still stored in their tier #2308 and Carry unused Income Tax trading losses forward once #2661.
• Apply the Universal Credit education condition #2806: uc_receiving_education reads an explicit is_in_full_time_education input for Universal Credit's education condition. These exemptions keep the local schemes' helper, which infers full-time study from current_education or in_HE. is_in_full_time_education stays false until a user or dataset sets it, so reading it here would end the student exemption for anyone without that input.

Axiom

axiom: TheAxiomFoundation/rulespec-uk#407 queued

rulespec-uk encodes none of HB reg 74, HB (SPC) reg 55, England's para 8 or Scotland's regs 48 and 90. Its Welsh Sch 1 para 3 and Sch 6 para 5 modules band a supplied gross income at 2026-27 amounts and defer the exemptions, the couple rule and apportionment. #407 holds the encoding brief, which binds the non-dependant's Universal Credit income to the award after the cap and before debt (uc_pilot_award_amount); no separately approved billed signed-encoder run exists for it.

Reproducer: policyengine_uk/tests/test_non_dependant_deduction_properties.py::test_band_edges_are_inclusive, policyengine_uk/tests/policy/baseline/finance/benefit/family/housing_benefit/non_dep_deduction/housing_benefit_non_dep_deduction_chain.yaml

🤖 Generated with Claude Code

[MaxGhenis]

Composition note: #2015 (stacked on #2009 → #2006) deletes the two household flags this PR reads. council_tax_reduction_household_has_pensioner becomes council_tax_reduction_pensioner and council_tax_reduction_household_has_non_dep_exemption becomes council_tax_reduction_applicant_has_non_dep_exemption; both are BenUnit, so each jointly liable claimant uses its own family. #2015 does not add the national applicant exemption; that stays here. Whichever lands second should do three things:

1. Read the applicant's own exemption flag for applicant_exempt.
2. Do not substitute the family flag into each_member_deducted: that is evaluated on the non-dependant family, and Sch 6 para 5(3) turns on the applicant's scheme. Instead build two household pools of non-dependant families' deductions, the higher member's and the sum for a non-dependant couple on UC. Each claimant takes the sum pool when it is in Wales and its own council_tax_reduction_pensioner is false, and the higher-member pool otherwise.
3. Pick England's pensioner scale in the person-level variables by country only. Each claim's own scheme already decides whether its award uses it. The two tests that pin "no national deduction in English working-age households" then check that the working-age award is unaffected instead.

See the "National schemes and the exemption" section of #2015. (Corrected per this PR's author.)

[MaxGhenis]

Response to review r1 of #2007 (59c7082)

The review asked for changes and was right on all five P1s. Each is fixed below with the law, the change, and a test that fails on 59c7082 and passes now.

#	Finding	Disposition	Change	Test
1	is_adult is not "claimant or partner" (an 18-year-old dependant's PIP exempted the claimant; a 17-year-old claimant's PIP did not)	Fixed	New helper is_claimant_or_partner: the benefit unit's head, or any member who is not an SSCBA s.142 child or qualifying young person (is_child_or_qualifying_young_person_for_child_benefit, already on main). That is how HB Regs 2006 regs 2(1) and 19 and the English and Welsh CTR regs (reg 2(1)) define a family's members other than claimant and partner. It is used in the HB claimant exemption and in council_tax_reduction_household_has_non_dep_exemption (which the local schemes also read)	non_dependant_deduction_review_cases.yaml: "A dependent 18-year-old's PIP does not exempt the claimant" (HB £6,232.20, CTR £691.60); "A 17-year-old claimant's PIP exempts their family"
2	A dependent child's income was added to the couple's	Fixed	Joint income (reg 74(4), para 8(4)) sums only the claimant and partner of the non-dependant's family. Other members are banded on their own income. One deduction per couple (reg 74(3)) covers only the couple; each other member is deducted separately	"A parent non-dependant is banded on their own income…" (HB £1,060.80, CTR £270.40); household_benefits_individual_non_dep_deduction.yaml "A dependent young person in the family is banded on their own income"
3	HB reg 6(6): a person on IS, JSA(IB) or ESA(IR) is not in remunerative work	Fixed	The HB individual deduction treats the claimant or partner of an IS, JSA(IB) or ESA(IR) award as not in remunerative work. CTR exempts those recipients outright, so it needs no equivalent	"On income-related ESA, 16 hours is not remunerative work" (£1,060.80)
4	A self-employment loss cancelled wages in the UC no-earned-income test	Fixed	has_earned_income: employment income plus self-employed earnings floored at nil (UC reg 57(2) step 3)	"A self-employed loss does not cancel wages…" (both exemptions false; HB £1,060.80, CTR £270.40)
5	Taxable total_income omits UC, tax credits and child benefit	Fixed	Gross income for a claimant or partner adds the family's UC (before the benefit cap, which would be circular through HB), CTC, WTC and child benefit to the couple's taxable income. The disability benefits disregarded by reg 74(9) are still excluded, since they are untaxed and not added	"Universal Credit counts towards gross income" (£290 a week, £3,346.20)

Also from the review:

• Benefit receipt (IS, JSA(IB), ESA(IR), SPC, UC) now exempts only the claimant or partner of the award, in both exemption variables.
• Two omissions are now listed as not modelled, because no input exists:
  • pension-age HB's 26-week deferral of a deduction increase (SI 2006/214 reg 59(10)-(13));
  • the CTR applicant exemption's protection while AA, DLA or PIP is suspended in hospital (para 8(6)).
• The property tests' generator now includes dependent young people with their own income (in full-time education, or on approved training and so not exempt) and self-employed losses. The oracles use the claimant-or-partner rule, reg 6(6) and the floored earnings.
• The Welsh "award of universal credit" reading stays as stated in the PR description, an interpretation.

Not changed: the review's UNVERIFIED items on impact (exact zeros, decomposition, poverty causation). The impact is rerun on the new head after the host is free (the Axiom build has priority until about 10:00Z). The PR description's impact section is replaced with the rerun.

[MaxGhenis]

Response to review r2 of #2007 (6257277)

The review asked for changes again and was right on all five P1s. Findings 2-5 are fixed in the next commit, each with a YAML test that fails on 6257277 (non_dependant_deduction_review_cases.yaml, "Round 2" section). Finding 1 is fixed by adopting #1896's is_claimant_or_partner when #1896 lands; it is about to merge, and its owner asked #2007 to use it.

#	Finding	Disposition	Change	Test
1	Claimant or partner via "head or not a child benefit QYP" misclassifies explicit young partners (HB reg 2(1) "partner"), and in the reverse direction a third adult; this reaches the English local schemes through the shared exemption flag	Fixed with #1896	The helper is replaced by #1896's is_claimant_or_partner, which caps the set at the head and one partner (SSCBA s.137 couple) and can be supplied as an input for explicit couples. The r1 original student case also resolves, since #1896 presumes a 19-year-old 26 years younger than the parent is their child	The r2 explicit-couple cases are added after the rebase, along with the r1 cases
2	"No earned income" missed SMP, relievable pension contributions and the minimum income floor (UC regs 55 and 62)	Fixed	has_earned_income: employment income plus SSP and SMP, less relievable pension contributions (reg 55(4)-(5)); self-employed earnings, a loss nil (reg 57(2)), with the minimum income floor where the UC model applies it (reg 62); and other paid work	SMP £8,000 → not exempt (£1,060.80/£270.40); wages all paid into a pension → exempt (£0/£0); MIF applies → not exempt (£1,060.80/£270.40)
3	ESA(IR) receipt was extended to the working partner (HB reg 2(3A): "payable to him")	Fixed	is_award_payee: IS, JSA(IB), ESA(IR) and SPC count only for the member who reports the award, or the head where none does; UC still counts for both joint claimants (HB reg 2(3B): entitlement). Used for the exemptions and for HB reg 6(6)	Recipient and partner earning £210 a week at 16 hours → HB £2,436.20, CTR £270.40
4	Pre-cap UC overstated gross income (UC reg 81)	Fixed	Gross income now uses UC after the benefit cap. The cap is applied to the capped benefits other than Housing Benefit, which a non-rent-liable family does not receive; this avoids the HB → UC → cap → HB cycle	Pre-cap £30,000, cap £20,000 → HB £5,470.40 (365 band), CTR £551.20
5	CTR's LGFA 1992 Sch 1 para 3 disregard (an adult for whom another person is entitled to child benefit) was omitted although inputs exist	Fixed	The CTR exemption adds an adult qualifying young person (child benefit, s.142) who is not the claimant or partner of their family	19-year-old on approved training with child benefit → CTR exempt, parent alone £270.40; HB still charges both (£3,497.00)

On the property tests, the review said the oracles repeat the implementation's classification. They now take the payee as the head (the generator reports no awards) and read the child benefit QYP flag from the model. After the #1896 rebase they read is_claimant_or_partner from the model, which is not code under test. The generator now draws dependent young people and losses. SMP, pension and MIF cases are pinned in YAML rather than generated.

[juaristi22]

Codex review — changes required

Reviewed commit e92b5d107d48fe6d6cd62927059e092a75d585c2. PARTIAL; 1 confirmed blocking finding(s). Independent code/test and policy/source reviews were consolidated for the changed behavior and affected dependencies.

code-1 — [P1] Replace the QYP-complement helper with actual claimant/partner roles

The current helper _non_dependants.py:28–36 still defines the claimant/partner set as the head or anybody who is not a Child Benefit child/qualifying young person. That is neither a relationship test nor a two-person limit. It can exclude an actual young partner in education and include a third adult. The helper controls the new disability exemptions, joint gross income and one-deduction-per-couple aggregation, so this is a material remaining integration blocker. The author's latest response also explicitly defers this finding to adoption of #1896; the captured head has not adopted it.

Executed illustration: a reported continuing HB award for an intended couple aged70/19, both parent-flagged, with the19-year-old in qualifying education and receiving standard PIP daily living, plus a separate40-year-old working non-dependant earning£30,000. The QYP complement excludes the young partner and sets the claimant exemption false. With £10,000 council rent and HB assessable income isolated at zero, the deduction is£6,232.20 and final HB£3,767.80. A control supplying the legally appropriate claimant/partner disability exemption gives deduction£0 and final HB£10,000. This snapshot lacks the canonical explicit claimant/partner input; the diagnostic's relationship is stated as the intended premise, while the code defect is the inability of this helper to honor that premise.

Adopt the canonical relationship/role variable after the prerequisite lands, then add explicit young-partner and third-adult regression cases through final awards. Do not repeat the other four r2 findings: the current tree now includes statutory sick/maternity pay, employed pension deductions and MIF; the benefit-payee test; UC after the benefit cap; and CTR's adult Child Benefit QYP exemption. Confidence: high for the current unresolved helper/integration defect.

Independent source review corroborates the actual-couple and claimant/partner conditions in HB regulation 74(3)–(6), HB interpretation and England CTR paragraph 8. The overlapping code and policy finding is counted once.

The current tree addresses round-two findings 2–5; this review does not repeat those stale blockers. Current 2026 scale values were corroborated. The remaining confirmed blocker is adoption of the canonical claimant/partner roles and coverage of their downstream HB/CTR behavior.

Outstanding evidence/decision:

• The prerequisite claimant/partner implementation is absent, so the eventual composed behavior cannot yet be tested.
• Historical CTR rates/dates for 2013–2025 were not all corroborated. Complete UC net-earnings treatment, including self-employed pension contributions, remains source-unresolved and is not asserted as a second confirmed defect.

Validation: 123 focused tests passed, including round-two regression tests. An executed controlled diagnostic isolates the missing partner disability exemption's final-HB effect. The intended relationship is an explicit scenario premise, and supplied benefits/HB assessable income isolate this path; the run does not establish any actual data record's demographics. Six official source originals were inspected and their cached bytes verified.

Focused tests used an existing cached Python 3.13 environment (Core 3.32.9, NumPy 2.1.3, pandas 2.3.1, microdf-python 1.2.1, Hypothesis 6.168.2, pytest 8.4.2) with this PR’s isolated source snapshot. No dependencies were installed; this was not a freshly synced lock environment or a full-suite/population run. This is a review comment, not a formal GitHub review vote.

Live check before posting (2026-10-02T10:41:08.415704+00:00): same commit, UNSTABLE; 0 failed checks; 1 pending checks.

[vahid-ahmadi]

Review pass (Claude Code, on Vahid's behalf) at e92b5d10

Short version: the rules match the law I read, and the tests pass locally. Two things before merge: the claimant-or-partner helper still needs #1896's role variable (the Codex review's P1, which I agree with and won't repeat), and one new should-fix on the student exemption's age default in the household calculator.

1. Should-fix: with no education input, every 18- or 19-year-old non-dependant counts as a full-time student and is exempt. housing_benefit_non_dep_deduction_exempt and the CTR equivalent use is_full_time_student_non_dep, which reads current_education. That variable's formula defaults ages 18–19 to TERTIARY when nothing is supplied (variables/household/demographic/current_education.py:36). The PR body notes this, but the effect in the household calculator is large. Probe at this head, 2026, a 45-year-old HB claimant (council rent £10,000) with a 19-year-old non-dependant earning £30,000 at 37.5 hours a week:

Non-dependant	current_education	Exempt	HB deduction
age 18, no input	TERTIARY (default)	yes	£0
age 19, no input	TERTIARY (default)	yes	£0
age 20, no input	NOT_IN_EDUCATION	no	£6,232.20
age 19, NOT_IN_EDUCATION supplied	NOT_IN_EDUCATION	no	£6,232.20

On main this non-dependant is charged, so the PR introduces the gap for HB and the national CTR schemes (the English local schemes already had it through the same helper). Datasets are unaffected, since the Enhanced FRS stores current_education. Suggested fix: base the student exemption on a stored or supplied education value only, not the age default. Alternatively, don't treat the default as full-time study for someone in remunerative work (16+ hours). Either way, add the 19-year-old case above as a test.

2. The claimant-or-partner helper (Codex P1). _non_dependants.py:28-36 is still "head or not a child-benefit QYP". The author has said it will switch to #1896's is_claimant_or_partner, and #1896 is still open, so this PR should wait for that rebase and add the explicit young-partner and third-adult cases the r2 response lists.

Checked and correct:

• Law: I read HB Regs 2006 reg 74 and HB (SPC) Regs reg 55 on legislation.gov.uk.
  • The bands are "not less than" at the lower edge, and the 2026-27 amounts are £20.40 to £131.45 on £192/£279/£365/£485/£605.
  • Couples get one deduction, the higher, on joint income (reg 74(3)-(4)).
  • The claimant exemption covers blindness, AA, the DLA care component, the PIP daily living component and AFIP (reg 74(6)).
  • The student exemption is reg 74(7)(c)-(e); the under-25 IS/JSA(IB)/ESA(IR)/UC-no-earned-income exemption is reg 74(8); SPC is reg 74(10) (reg 55(9) for pension age).
  • England CTR Sch 1 para 8 has £5.20/£10.60/£13.30/£15.95 on £279/£485/£605, with its own para 8(7)-(8) exemptions, including the LGFA Sch 1 disregard and the UC limb.
• Remunerative work: banding applies only at 16+ hours and not on an income-related benefit (reg 6(6)); anyone else pays the (1)(b) amount.
• has_earned_income counts miscellaneous_income, the same as the UC model's own uc_mif_capped_earned_income, so it is consistent within the model.
• Tests at this head: the HB and local-authority YAML suites pass 205/205, and test_non_dependant_deduction_properties.py passes 6/6. CI's Test job was still running when I checked; the other six checks pass.

[MaxGhenis]

Composition note from #2078 (stacked on #2009), which makes the CTR means test assess the applicant and partner rather than the benefit unit's claimant and partner.

#2078 changes council_tax_reduction_household_has_non_dep_exemption to read is_council_tax_reduction_applicant_or_partner (new Person variable) in place of is_claimant_or_partner, following "the applicant or his partner" in SI 2012/2885 Sch 1 para 8(6). The two differ where the household head is liable but is not the benefit unit's claimant or partner. Example: a blind grandmother head sharing a benefit unit with a young couple, who were not exempt before.

When this PR's national exemption (council_tax_reduction_non_dep_deduction_exempt) composes with #2078, it should use the same identity for the applicant or partner. #2015 replaces the household flag with a per-family one and gets the same note.