Route historical under-65 pensioner Housing Benefit allowances separately #2230

Summary

Approved plan B1 routes historical qualifying pensioner families below age 65 to their separate lower allowance. Add exactly three household-category parameter documents, modify the existing applicable-amount formula and tests, and add a changelog: six files, zero inputs. Stack on #2207 rather than repeat its higher-category correction. GB removal is 6 December 2018; NI's April 2019 replacement table is independently verified. GB 2015 pensioner Housing Benefit allowances (Single/lone parent under 65 £151.20, couple £230.85); GB 2016 pensioner Housing Benefit allowances (Lower single £155.60, couple £237.55); GB 2017 pensioner Housing Benefit allowances (Lower single £159.35, couple £243.25); GB 2018 pensioner Housing Benefit allowances (Lower single £163.00, couple £248.80); GB removal of under-65 category (Regulations 1(2)(b) and 7(7): 6 December 2018); NI 2018 lower pensioner Housing Benefit allowances (Under-65 single £163.00, couple £248.80; original Order avoids stale consolidated table); NI 2019 replacement pensioner Housing Benefit table (Articles 1(1)(a), 24(5)(a), Schedule 4: 1 April 2019 table has no lower category); NI 2015 lower pensioner allowances (Single/lone parent £151.20, couple £230.85); NI 2016 lower pensioner allowances (Regulation 6(3): £155.60 and £237.55); NI 2017 lower pensioner allowances (Single/lone parent £159.35, couple £243.25)

Audited model surface

• Audited release: policyengine-uk 2.106.1
• Audit unit: variable:housing_benefit_applicable_amount
• Last model modification: 2024-07-15
• Explicitly reviewed units:
  • variable:housing_benefit_applicable_amount — last model modification: 2024-07-15
• Audit date: 2026-10-09
• Periods reviewed: Fiscal years 2015–2019 and later historical-routing exclusion
• Jurisdictions: Great Britain and Northern Ireland

Findings and implementation parts

1. Selecting the higher pensioner allowance for every qualifying pensioner incorrectly overstates the historical below-65 category.

Sources: GB 2015 pensioner Housing Benefit allowances (Single/lone parent under 65 £151.20, couple £230.85); GB 2016 pensioner Housing Benefit allowances (Lower single £155.60, couple £237.55); GB 2017 pensioner Housing Benefit allowances (Lower single £159.35, couple £243.25); GB 2018 pensioner Housing Benefit allowances (Lower single £163.00, couple £248.80); GB removal of under-65 category (Regulations 1(2)(b) and 7(7): 6 December 2018); NI 2018 lower pensioner Housing Benefit allowances (Under-65 single £163.00, couple £248.80; original Order avoids stale consolidated table); NI 2019 replacement pensioner Housing Benefit table (Articles 1(1)(a), 24(5)(a), Schedule 4: 1 April 2019 table has no lower category); NI 2015 lower pensioner allowances (Single/lone parent £151.20, couple £230.85); NI 2016 lower pensioner allowances (Regulation 6(3): £155.60 and £237.55); NI 2017 lower pensioner allowances (Single/lone parent £159.35, couple £243.25)

• Add allowances/{single,lone_parent,couple}/aged_under_65.yaml as nodes containing amount and dated GB/NI age limits, route only pension-age-regulation families by eldest claimant/partner age, retain explicit zero parameter reforms, and add focused annual-convention tests/changelog. Existing Correct historical Housing Benefit pensioner allowances #2207 owns higher 2015–18 values; Split pension-age Housing Benefit allowances by when State Pension age was attained #1913 owns later cohorts. No CTR changes or new input. GB 2015 pensioner Housing Benefit allowances (Single/lone parent under 65 £151.20, couple £230.85); GB 2016 pensioner Housing Benefit allowances (Lower single £155.60, couple £237.55); GB 2017 pensioner Housing Benefit allowances (Lower single £159.35, couple £243.25); GB 2018 pensioner Housing Benefit allowances (Lower single £163.00, couple £248.80); GB removal of under-65 category (Regulations 1(2)(b) and 7(7): 6 December 2018); NI 2018 lower pensioner Housing Benefit allowances (Under-65 single £163.00, couple £248.80; original Order avoids stale consolidated table); NI 2019 replacement pensioner Housing Benefit table (Articles 1(1)(a), 24(5)(a), Schedule 4: 1 April 2019 table has no lower category); NI 2015 lower pensioner allowances (Single/lone parent £151.20, couple £230.85); NI 2016 lower pensioner allowances (Regulation 6(3): £155.60 and £237.55); NI 2017 lower pensioner allowances (Single/lone parent £159.35, couple £243.25)
  • Add or update reference at policyengine_uk/variables/gov/dwp/housing_benefit/housing_benefit_applicable_amount.py → references and historical lower/higher category selection using GB 2015 pensioner Housing Benefit allowances (Single/lone parent under 65 £151.20, couple £230.85); GB 2016 pensioner Housing Benefit allowances (Lower single £155.60, couple £237.55); GB 2017 pensioner Housing Benefit allowances (Lower single £159.35, couple £243.25); GB 2018 pensioner Housing Benefit allowances (Lower single £163.00, couple £248.80); GB removal of under-65 category (Regulations 1(2)(b) and 7(7): 6 December 2018); NI 2018 lower pensioner Housing Benefit allowances (Under-65 single £163.00, couple £248.80; original Order avoids stale consolidated table); NI 2019 replacement pensioner Housing Benefit table (Articles 1(1)(a), 24(5)(a), Schedule 4: 1 April 2019 table has no lower category); NI 2015 lower pensioner allowances (Single/lone parent £151.20, couple £230.85); NI 2016 lower pensioner allowances (Regulation 6(3): £155.60 and £237.55); NI 2017 lower pensioner allowances (Single/lone parent £159.35, couple £243.25).

Uncertainties and exclusions

Amounts follow the existing 30-April annual sampling convention, not a daily entitlement reconstruction. Raw calendar end dates are encoded in age limits; no partial-year age/award-history input is added. NI matching 2015–17 original Orders must be cited. CTR historical routes are outside this approved subset.