diff --git a/README.md b/README.md
index ccf3d20..e68e4d4 100644
--- a/README.md
+++ b/README.md
@@ -64,6 +64,39 @@ func main() {
 }
 ```
 
+## Showing The Expiry Date
+
+`ActivateKey` and `FloatingCheckout` return `ExpirationDate`: when the license
+expires, as an ISO 8601 string, or `nil` if it never expires. On
+`FloatingCheckoutResponse` this is the license expiry; `ExpiresAt` is the
+floating seat lease.
+
+```go
+res, err := client.ActivateKey(keymint.ActivateKeyParams{
+    ProductID:  productId,
+    LicenseKey: licenseKey,
+    HostID:     keymint.String(hostId),
+})
+if err != nil {
+    // handle error
+}
+
+if res.ExpirationDate == nil {
+    fmt.Println("License never expires")
+} else if exp, err := time.Parse(time.RFC3339, *res.ExpirationDate); err == nil {
+    daysLeft := int(math.Ceil(time.Until(exp).Hours() / 24))
+    if daysLeft < 0 {
+        daysLeft = 0
+    }
+    fmt.Printf("Expires %s (%d days left)\n", exp.Format("2006-01-02"), daysLeft)
+}
+```
+
+Store the last `ExpirationDate` your app received. An expired license fails
+activation with the same generic error as an invalid key, so the stored date
+lets your app tell the user the license expired on that date rather than
+calling the key invalid.
+
 ## Machine Identity
 Keymint provides utilities to uniquely identify machines for node-locking:
 
diff --git a/Types.go b/Types.go
index 873c390..e496065 100644
--- a/Types.go
+++ b/Types.go
@@ -140,6 +140,11 @@ type ActivateKeyResponse struct {
 	Version map[string]interface{} `json:"version,omitempty"`
 	// AllowedHosts is an optional list of authorized machine IDs.
 	AllowedHosts []string `json:"allowedHosts,omitempty"`
+	// ExpirationDate is when the license expires, as an ISO 8601 string
+	// (e.g. "2027-03-01T00:00:00.000Z"). It is nil when the license never
+	// expires. An expired license fails activation with the generic
+	// invalid-key error, so store the last value received.
+	ExpirationDate *string `json:"expirationDate,omitempty"`
 }
 
 // DeactivateKeyParams represents parameters for the deactivateKey API endpoint.
@@ -515,6 +520,9 @@ type FloatingCheckoutResponse struct {
 	LicenseeName *string `json:"licenseeName,omitempty"`
 	// LicenseeEmail is the optional email of the customer licensee.
 	LicenseeEmail *string `json:"licenseeEmail,omitempty"`
+	// ExpirationDate is when the license expires, as an ISO 8601 string, or
+	// nil when it never expires. It is not the seat lease; see ExpiresAt.
+	ExpirationDate *string `json:"expirationDate,omitempty"`
 }
 
 // FloatingHeartbeatParams represents parameters for the floating license heartbeat API endpoint.
diff --git a/contract_test.go b/contract_test.go
index e13b405..1374e2c 100644
--- a/contract_test.go
+++ b/contract_test.go
@@ -167,3 +167,67 @@ func TestApiErrorsExposeNestedMessage(t *testing.T) {
 		t.Fatalf("status not captured: %#v", apiErr.Status)
 	}
 }
+
+// expirationCases covers the three shapes the API can send: a date, an
+// explicit null (never expires), and an older server that omits the field.
+var expirationCases = []struct {
+	name string
+	body string
+	want *string
+}{
+	{"date", `"expirationDate":"2027-03-01T00:00:00.000Z",`, String("2027-03-01T00:00:00.000Z")},
+	{"null", `"expirationDate":null,`, nil},
+	{"absent", ``, nil},
+}
+
+func checkExpiration(t *testing.T, got, want *string) {
+	t.Helper()
+	switch {
+	case want == nil && got != nil:
+		t.Fatalf("expected nil ExpirationDate, got %q", *got)
+	case want != nil && got == nil:
+		t.Fatalf("expected ExpirationDate %q, got nil", *want)
+	case want != nil && *got != *want:
+		t.Fatalf("expected ExpirationDate %q, got %q", *want, *got)
+	}
+}
+
+func TestActivateKeyDeserializesExpirationDate(t *testing.T) {
+	for _, tc := range expirationCases {
+		t.Run(tc.name, func(t *testing.T) {
+			c, done := newTestClient(t, func(w http.ResponseWriter, r *http.Request) {
+				w.Header().Set("Content-Type", "application/json")
+				_, _ = w.Write([]byte(`{"code":0,"message":"License valid",` + tc.body + `"metadata":{"hostId":"h1"}}`))
+			})
+			defer done()
+
+			res, err := c.ActivateKey(ActivateKeyParams{ProductID: "p", LicenseKey: "k", HostID: String("h1")})
+			if err != nil {
+				t.Fatalf("ActivateKey failed: %v", err)
+			}
+			checkExpiration(t, res.ExpirationDate, tc.want)
+		})
+	}
+}
+
+func TestFloatingCheckoutDeserializesExpirationDate(t *testing.T) {
+	for _, tc := range expirationCases {
+		t.Run(tc.name, func(t *testing.T) {
+			c, done := newTestClient(t, func(w http.ResponseWriter, r *http.Request) {
+				w.Header().Set("Content-Type", "application/json")
+				_, _ = w.Write([]byte(`{"code":0,"message":"ok","sessionId":"s","sessionSecret":"sec","nextNonce":"n",` +
+					`"expiresAt":"2026-10-26T12:00:00.000Z","heartbeatInterval":60,` + tc.body + `"currentSessions":1,"maxSessions":5}`))
+			})
+			defer done()
+
+			res, err := c.FloatingCheckout(FloatingCheckoutParams{ProductID: "p", LicenseKey: "k", HostID: "h"})
+			if err != nil {
+				t.Fatalf("FloatingCheckout failed: %v", err)
+			}
+			if res.ExpiresAt != "2026-10-26T12:00:00.000Z" {
+				t.Fatalf("seat lease ExpiresAt changed: %q", res.ExpiresAt)
+			}
+			checkExpiration(t, res.ExpirationDate, tc.want)
+		})
+	}
+}