[PavelMakarchuk]

Fixes #10506.

Summary

For 2018–2022, Form IT-213 Worksheet A computes the pre-TCJA federal credit for every child on form line 4, including children under 4, and form lines 9–12 then multiply the result by line 5 (children aged 4–16) / line 4. ny_ctc_pre_2024 instead dropped the children under 4 before the federal computation, so the phase-out and the tax limit fell only on the older children.

Changes

• ny_ctc_pre_2024: the pinned pre-TCJA branch no longer overrides ctc_individual_maximum, so the federal credit counts every child who qualifies for it (Worksheet A line 1). Under the 2017 pin the ODC amount is $0, so the branch's ctc_individual_maximum equals ctc_child_individual_maximum.
• The federal credit is multiplied by (children aged at least minimum_age) / (children who qualify for the federal credit) before the 33% (form lines 9–13). From 2023, minimum_age is 0, so the share is 1 and nothing changes.
• The $100 minimum (lines 14–15) still uses the line 5 count.

Tests

New cases in ny_ctc_pre_2024.yaml. Each expected value comes from the IT-213 worksheet arithmetic, written out in the test comments:

Case	Expected	Before
2022 HOH, ages 2 and 10, $85,000 wages (phase-out)	247.50	165.00
2022 HOH, ages 2 and 10, $40,000 wages (below threshold)	330.00	330.00
2022 HOH, ages 2 and 10, $26,000 pension (tax limit, no ACTC)	108.90	217.80
2021 MFJ, ages 3 and 8, $120,500 wages (phase-out, round-up)	239.25	148.50
2022 child aged 2 only	0 (not eligible)	0

The three cases with a changed value fail on main and pass on this branch. The issue's example (head of household, $85,000, ages 2 and 10) now gives 247.50 in each year 2018–2022, with the issue's federal tax amounts (9,288; 9,101; 8,945; 8,860; 8,549). Its controls still give 165.00 (one child aged 10, $85,000) and 330.00 (ages 2 and 10, $50,000).

Locally, after rebasing on main with #10280, all 248 YAML test files that refer to New York (3,060 tests, including ny_ctc.yaml, the NY integration tests and the NY contrib reforms) pass.

Not in this PR

• 2021 children aged 17. The 2021 IT-213 instructions put them on line 4 ("While line 4 includes all children less than 18 years old, line 5 must only include children at least four but less than 17 years old"). The same instructions say the age limit "will remain at less than 17 years old" for the NYS credit, and §606(c-1) refers to section 24 as it existed before Public Law 115-97, whose qualifying child is under 17. The 2017 pin keeps the under-17 limit, so this branch leaves 17-year-olds off line 4. For 2021, head of household, $85,000, children aged 10 and 17, this branch gives 165.00; the 2021 line 4 instruction gives 247.50. This needs a separate decision.
• Form line 3 allows the $100 minimum at "$75,000 or less" (Worksheet A line 4 asks whether AGI is "more than" the threshold), but the formula uses agi < federal_threshold. This changes only a filer with AGI exactly at the threshold.
• The form uses whole dollars; PE does not round, as before.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (909176a) to head (4c2c3a0).
⚠️ Report is 706 commits behind head on main.

Additional details and impacted files

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  Coverage   100.00%   100.00%           
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  Files            4         1    -3     
  Lines           76        46   -30     
  Branches         2         3    +1     
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- Hits            76        46   -30     

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[hua7450]

Approving at 4c2c3a0. Thanks, Pavel.

This follows IT-213. Worksheet A computes the federal credit for every child on form line 4, and lines 9 to 12 multiply it by line 5 / line 4 before the 33% on line 13. Dropping the ctc_individual_maximum override in the pinned branch is safe, because the 2017 pin has no ODC. The share has a guard for units with no federal qualifying children. The $100 minimum still uses line 5. I recomputed the five new cases from the worksheet arithmetic, and they match.

Optional nits:

1. 2015 to 2017 also change. The proration runs in both branches. In 2015 to 2017 pre_tcja is false, and minimum_age is 4 there because the 2018 value is backdated. So the unpinned branch is now prorated too. That is correct, since the 2017 IT-213 has the same lines 9 to 12, and it fixes a larger overstatement on main. For example, 2017, head of household, $40,000, children 2 and 10: 330 at head, 660 on main, 330 on the form. The 2021 supplemental payment (ny_additional_ctc, 25% of the credit) moves with it. The title, changelog and body say 2018 to 2022. "Through 2022", plus one 2017 case like the one above, would record this.
2. 2021 17-year-olds. The PR body leaves this for a separate decision. CONTRIBUTING's statute-first rule already decides it: §606(c-1) refers to section 24 before P.L. 115-97, whose qualifying child is under 17, and the code follows that. Saying so in the body, with a register entry and a # Source conflict marker on the federal_children line, would record the conflict with the 2021 line 4 instruction.
3. Tests.
   • No mixed-age case has a positive refundable part (Worksheet C, form line 7), so nothing shows that the line 8 total is prorated. For example, 2022, head of household, $8,000 of wages, children 2 and 10 gives 123.75.
   • The new cases are inserted mid-file without "Case N," names.

Follow-ups, outside this PR (all the same on main):

• The 2017 pin carries child_ssn_requirement_applies (true from 2018, backdated), so a child with only an ITIN is left off lines 4 and 5. Pre-TCJA 24(e) needs only a TIN. This also reaches 2023 and 2024.
• Before 2018 the federal amount is ctc before the tax limit, with no ACTC. The 2017 form uses line 6 (credit allowed) plus line 7 (ACTC).
• The $100 minimum uses agi < federal_threshold. Form line 3 allows it at "$75,000 or less".