Correct the protected pension-age Housing Benefit allowance projection #2154

Summary

PolicyEngine UK 2.106.1 does not faithfully represent the weekly Housing Benefit personal allowance selected by gov.dwp.housing_benefit.allowances.single.aged. The parameter back-carries the 2019-20 rate of £181 into 2015-16 through 2018-19, omits the 2020-21 rate of £187.75, and stores £239.20 instead of the enacted £244.40 for 2025-26. Pull request #1925 already owns those explicit-rate corrections. From April 2021, the selected series is only the protected rate for a single claimant or lone parent who attained pensionable age before 1 April 2021; the lower post-2021 rate is the Pension Credit standard minimum guarantee. The protected 2026-27 rate is the £238.00 guarantee plus the retained £17.96 maximum Savings Credit uplift, rounded to £256.00. Projecting that composite rate wholly by CPI from 2027-28 therefore misses the guarantee's earnings basis. A faithful forecast proxy should project the guarantee with the non-negative May-to-July earnings input used for the following April's statutory review, project the retained uplift with the preceding September CPI input, and combine the components; it is not an enacted future amount. Benefit and pension rates 2020 to 2021 (Housing Benefit, personal allowances, pensioner, single and lone-parent row); The Housing Benefit (Persons who have attained the qualifying age for state pension credit) (Amendment) Regulations 2021 (regulation 2(2)(a) and (3), inserted Schedule 3 paragraph 1(1)(c)); Explanatory Note to S.I. 2021/188 (paragraphs 1 to 3); The Housing Benefit (Persons who have attained the qualifying age for state pension credit) (Amendment) Regulations (Northern Ireland) 2021 (explanatory memorandum paragraphs 2.1 and 2.2); Benefit and pension rates 2025 to 2026 (Housing Benefit, personal allowances, pensioner rows for 2024-25 and 2025-26); The Social Security Benefits Up-rating Order 2025 (Schedule 6, paragraph 6, Schedule 3 Part 1 table paragraph 1(1)(b) and (c)); The Social Security Benefits Up-rating Order (Northern Ireland) 2025 (Schedule 6, paragraph 5(a), Schedule 4 Part 1 table paragraph 1(1)(b) and (c)); A14/2025 Housing Benefit uprating for the financial year ending March 2027 (paragraphs 4 to 7 and 20); The Social Security Benefits Up-rating Order 2026 (Schedule 6, paragraph 6, Schedule 3 Part 1 table paragraph 1(1)(b) and (c)); The Social Security Benefits Up-rating Order (Northern Ireland) 2026 (Schedule 6, paragraph 5(a), Schedule 4 Part 1 table paragraph 1(1)(b) and (c)); KAC3 Average weekly earnings, whole economy, total pay (May to July annual growth series, latest provisional release); D7G7 Consumer Prices Index annual rate (September annual CPI rate series)

Audited model surface

• Audited release: policyengine-uk 2.106.1
• Audit unit: parameter:gov.dwp.housing_benefit.allowances.single.aged
• Last model modification: 2026-05-23
• Audit date: 2026-10-05
• Periods reviewed: 2015-16 through 2026-27 explicit weekly amounts and cohort mechanics, 2027-28 and later projection behavior
• Jurisdictions: Great Britain, Northern Ireland

Findings and implementation parts

1. The 2025-26 weekly amount is £4.80 too low and the single undifferentiated branch cannot represent the two pension-age tiers used before April 2019. The release also omits the 2020-21 £187.75 amount. Pull request #1925 owns the explicit 2020 and 2025 corrections and documents the remaining pre-2019 structural gap, so this audit must not duplicate those edits.

Sources: A13/2015 Housing Benefit uprating for 2016-17 (Appendix B, pension-age personal allowances for April 2015 and April 2016); A10/2017 Housing Benefit uprating for 2018-19 (Appendix B, pages 10 to 11, pension-age personal allowances for April 2017 and April 2018); A8/2018 Housing Benefit uprating for 2019-20 (Appendix B, Housing Benefit for people who have reached Pension Credit qualifying age, single claimant or lone parent row); Benefit and pension rates 2020 to 2021 (Housing Benefit, personal allowances, pensioner, single and lone-parent row); Benefit and pension rates 2025 to 2026 (Housing Benefit, personal allowances, pensioner rows for 2024-25 and 2025-26); The Social Security Benefits Up-rating Order 2025 (Schedule 6, paragraph 6, Schedule 3 Part 1 table paragraph 1(1)(b) and (c)); The Social Security Benefits Up-rating Order (Northern Ireland) 2025 (Schedule 6, paragraph 5(a), Schedule 4 Part 1 table paragraph 1(1)(b) and (c))

• Preserve pull request Set DWP benefit rates to the announced amounts, not CPI projections #1925's correction to £187.75 for 2020-21 and £244.40 for 2025-26, its corrected GB and Northern Ireland sources, and its description limiting this branch to the protected pre-April 2021 cohort. Do not duplicate those changes in this correction. Benefit and pension rates 2020 to 2021 (Housing Benefit, personal allowances, pensioner, single and lone-parent row); Benefit and pension rates 2025 to 2026 (Housing Benefit, personal allowances, pensioner rows for 2024-25 and 2025-26); The Social Security Benefits Up-rating Order 2025 (Schedule 6, paragraph 6, Schedule 3 Part 1 table paragraph 1(1)(b) and (c)); The Social Security Benefits Up-rating Order (Northern Ireland) 2025 (Schedule 6, paragraph 5(a), Schedule 4 Part 1 table paragraph 1(1)(b) and (c))
  • Add or update reference at policyengine_uk/parameters/gov/dwp/housing_benefit/allowances/single/aged.yaml → description, values.2020-04-01, values.2025-04-01, and metadata.reference using Benefit and pension rates 2020 to 2021 (Housing Benefit, personal allowances, pensioner, single and lone-parent row); Benefit and pension rates 2025 to 2026 (Housing Benefit, personal allowances, pensioner rows for 2024-25 and 2025-26); The Social Security Benefits Up-rating Order 2025 (Schedule 6, paragraph 6, Schedule 3 Part 1 table paragraph 1(1)(b) and (c)); The Social Security Benefits Up-rating Order (Northern Ireland) 2025 (Schedule 6, paragraph 5(a), Schedule 4 Part 1 table paragraph 1(1)(b) and (c)).

2. From 2027-28 the release projects all £256.00 by CPI. The protected amount instead combines the Pension Credit standard minimum guarantee with the retained maximum Savings Credit uplift. DWP increased those components by 4.8% and 3.8% respectively for 2026-27, producing £238.00 plus £17.96 and the rounded £256.00 protected allowance. A single CPI index therefore understates the first projected allowance when forecast earnings exceed forecast CPI, while applying earnings to the whole allowance would overstate the Savings Credit component.

Sources: The Housing Benefit (Persons who have attained the qualifying age for state pension credit) (Amendment) Regulations 2021 (regulation 2(2)(a) and (3), inserted Schedule 3 paragraph 1(1)(c)); Explanatory Note to S.I. 2021/188 (paragraphs 1 to 3); The Housing Benefit (Persons who have attained the qualifying age for state pension credit) (Amendment) Regulations (Northern Ireland) 2021 (explanatory memorandum paragraphs 2.1 and 2.2); A14/2025 Housing Benefit uprating for the financial year ending March 2027 (paragraphs 4 to 7 and 20); The Social Security Benefits Up-rating Order 2026 (Schedule 6, paragraph 6, Schedule 3 Part 1 table paragraph 1(1)(b) and (c)); The Social Security Benefits Up-rating Order (Northern Ireland) 2026 (Schedule 6, paragraph 5(a), Schedule 4 Part 1 table paragraph 1(1)(b) and (c)); Social Security Administration Act 1992 section 150 (section 150(2), (3), (5), and (7))

• Add a forecast index for the protected pension-age Housing Benefit allowance that combines a £238 guarantee component projected by the non-negative May-to-July earnings input used for the following April's statutory review with the remaining £18 of the rounded £256 allowance projected by the preceding September CPI input. Use published ONS observations where available and the repository's OBR forecast bridge otherwise. Apply it after the last enacted rate, label it as a forecast proxy rather than enacted law, embed the GB and Northern Ireland cohort and uprating sources, and test the raw 2026 amount, the first projected value, and both component calculations. Explanatory Note to S.I. 2021/188 (paragraphs 1 to 3); A14/2025 Housing Benefit uprating for the financial year ending March 2027 (paragraphs 4 to 7 and 20); The Social Security Benefits Up-rating Order 2026 (Schedule 6, paragraph 6, Schedule 3 Part 1 table paragraph 1(1)(b) and (c)); The Social Security Benefits Up-rating Order (Northern Ireland) 2026 (Schedule 6, paragraph 5(a), Schedule 4 Part 1 table paragraph 1(1)(b) and (c)); KAC3 Average weekly earnings, whole economy, total pay (May to July annual growth series, latest provisional release); D7G7 Consumer Prices Index annual rate (September annual CPI rate series)
  • Add or update reference at policyengine_uk/parameters/gov/dwp/housing_benefit/allowances/single/aged.yaml → metadata.uprating using Explanatory Note to S.I. 2021/188 (paragraphs 1 to 3); A14/2025 Housing Benefit uprating for the financial year ending March 2027 (paragraphs 4 to 7 and 20); The Social Security Benefits Up-rating Order 2026 (Schedule 6, paragraph 6, Schedule 3 Part 1 table paragraph 1(1)(b) and (c)); The Social Security Benefits Up-rating Order (Northern Ireland) 2026 (Schedule 6, paragraph 5(a), Schedule 4 Part 1 table paragraph 1(1)(b) and (c)); KAC3 Average weekly earnings, whole economy, total pay (May to July annual growth series, latest provisional release); D7G7 Consumer Prices Index annual rate (September annual CPI rate series).
  • Add or update reference at policyengine_uk/parameters/gov/dwp/housing_benefit/allowances/single/aged.yaml → description and metadata.reference using Explanatory Note to S.I. 2021/188 (paragraphs 1 to 3); A14/2025 Housing Benefit uprating for the financial year ending March 2027 (paragraphs 4 to 7 and 20); The Social Security Benefits Up-rating Order 2026 (Schedule 6, paragraph 6, Schedule 3 Part 1 table paragraph 1(1)(b) and (c)); The Social Security Benefits Up-rating Order (Northern Ireland) 2026 (Schedule 6, paragraph 5(a), Schedule 4 Part 1 table paragraph 1(1)(b) and (c)); KAC3 Average weekly earnings, whole economy, total pay (May to July annual growth series, latest provisional release); D7G7 Consumer Prices Index annual rate (September annual CPI rate series).

Projection behavior

• gov.dwp.housing_benefit.allowances.single.aged uses gov.benefit_uprating_cpi after 2026-04-01 (first projected date 2027-04-01): incorrect_in_release. Applying CPI to the whole protected allowance ignores that its guarantee component follows Pension Credit while only the retained maximum Savings Credit uplift follows CPI; the first projected value should use a component-weighted forecast proxy. Sources: Explanatory Note to S.I. 2021/188 (paragraphs 1 to 3); A14/2025 Housing Benefit uprating for the financial year ending March 2027 (paragraphs 4 to 7 and 20); The Social Security Benefits Up-rating Order 2026 (Schedule 6, paragraph 6, Schedule 3 Part 1 table paragraph 1(1)(b) and (c)); The Social Security Benefits Up-rating Order (Northern Ireland) 2026 (Schedule 6, paragraph 5(a), Schedule 4 Part 1 table paragraph 1(1)(b) and (c))

Uncertainties and exclusions

No 2027-28 protected Housing Benefit amount had been enacted or published by 5 October 2026. The component-weighted index is therefore a transparent forecast proxy: the future order may use a different earnings estimate, apply a discretionary increase, or round differently. The £18 projected Savings Credit component allocates the four-pence statutory rounding difference in the enacted £256 rate to the retained uplift; using the published £17.96 maximum instead would change the first forecast by only a few pence. Published observations can replace forecast inputs before the eventual order is made; on the audit date, the May-to-July 2026 earnings estimate was provisional and September 2026 CPI had not been published. This review does not certify the formula's cohort selection, Council Tax Reduction's legal reuse of Housing Benefit rates, couple rates, polygamous marriages, premiums, income rules, or entitlement. Pull request #1925 owns the explicit 2020-21 and 2025-26 corrections. The corrective PR from this review should be rebased after #1925. Pull request #2146 should share the current main branch's statutory earnings input when it rebases, rather than maintain a second earnings-proxy series.