Keep Working Tax Credit age and hours conditions on the same worker

changelog.d/2042.fixed.md

@@ -0,0 +1 @@
+- Corrected Working Tax Credit eligibility so age, disability and hours conditions applied to the same claimant or partner, while preserving the parental combined-hours and partner-exception routes.

docs/book/programs/gov/dwp/tax-credits.md

@@ -47,7 +47,25 @@ from the means test, gated by the `would_claim_WTC` take-up input.
 The `min_hours` tree (`min_hours/default.yaml`, `lower.yaml`,
 `old_age.yaml`, `couple_with_children.yaml`) encodes the bands that gate
 WTC eligibility — typically 30 hours/week for adults with no kids, 16 for
-lone parents, with a lower band for over-60s.
+lone parents, with a lower band for workers aged 60 or over.
+
+For the joint-claim rules from 6 April 2012, an individual's own age or
+disability must qualify that individual's hours. Two childless workers cannot
+pool 15 hours each to meet the ordinary 30-hour route, and a nonworking
+partner cannot lend their age or disability to the worker. Parents can combine
+24 hours, with at least one claimant working 16 hours. Hours worked by a
+child or other dependant do not count towards that total. The `min_age` and
+`min_age_without_children_or_disability` parameters provide the 16-year and
+25-year thresholds; the existing `min_hours.old_age` parameter provides 60.
+Native annual formula selection retains the earlier formula for a year whose
+start precedes 6 April 2012; this change does not certify all earlier rules.
+
+`is_disabled_for_benefits` remains a generic proxy for the statutory disabled
+worker conditions. For parents, the model also retains its existing proxy
+for an exception based on the other partner's disability. These flags do not
+encode all regulation 9 or regulation 13 tests, incapacity, hospital or prison
+status, carer's allowances, or the expected four-week and paid-work conditions.
+The reported-award, migration, take-up and scheme-closure rules remain separate.
 
 ## Child Tax Credit (CTC)
 

policyengine_uk/parameters/gov/dwp/tax_credits/working_tax_credit/min_age.yaml

@@ -0,0 +1,9 @@
+description: Minimum age for the specified Working Tax Credit 16-hour and parental routes.
+values:
+  # Joint-claim variations inserted by SI 2012/848 from 6 April 2012.
+  2012-04-06: 16
+metadata:
+  unit: year
+  reference:
+    title: The Working Tax Credit (Entitlement and Maximum Rate) Regulations 2002, regulation 4
+    href: https://www.legislation.gov.uk/uksi/2002/2005/regulation/4/2024-04-06

policyengine_uk/parameters/gov/dwp/tax_credits/working_tax_credit/min_age_without_children_or_disability.yaml

@@ -0,0 +1,9 @@
+description: Minimum age for the ordinary Working Tax Credit 30-hour route without children or a qualifying disability.
+values:
+  # Joint-claim variations inserted by SI 2012/848 from 6 April 2012.
+  2012-04-06: 25
+metadata:
+  unit: year
+  reference:
+    title: The Working Tax Credit (Entitlement and Maximum Rate) Regulations 2002, regulation 4
+    href: https://www.legislation.gov.uk/uksi/2002/2005/regulation/4/2024-04-06