Correct Housing Benefit applicable amounts, disregards, capital and non-dependants

changelog.d/2197.fixed.md

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+- Corrected Housing Benefit historical allowances and non-dependant scales, and the pre-November-2009 pension-age capital threshold.
+- Added child applicable amounts, protected family and child-disability premiums, and the claimant-specific ESA age exception.
+- Corrected childcare qualification and income limits, special/permitted-work earnings disregards, capital exclusions and ownership treatment, and the LISA medical exception.
+- Added remaining non-dependant exceptions and claimant-specific pension-age postponement, with government references and focused regression tests.
+- Corrected connected Council Tax Reduction historical under-65 pensioner routing and updated existing regression tests for the changed Housing Benefit rules.

docs/engineering/housing-benefit-assessment.md

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+# Housing Benefit assessment facts and timing
+
+Housing Benefit calculations use individual policy parameters and the existing
+person, benefit-unit and household entities. Additional facts are needed where
+annual income, age and household wealth cannot establish statutory eligibility.
+These inputs do not change a claimant's circumstances automatically.
+
+## Annual amounts and dated facts
+
+Weekly amounts become annual amounts using the model's 52-week convention.
+Ordinary parameters retain the model's 30 April fiscal-year sampling. Preserved
+Boolean schedules and `fiscal_year_segments` handle the December 2018 removal
+of the under-65 allowance, the two-child restriction and its removal, and
+jurisdiction-specific family-premium abolition. Those calculations hold supplied
+family facts fixed and apply the rule separately in each segment before averaging.
+They do not multiply a Boolean input by an assumed share of a year.
+
+`housing_benefit_assessment_date` defaults to 6 October, matching annual age
+inputs. It is the date for reported childcare status, retained capital and pending
+non-dependant changes. The resulting point-in-time weekly calculation is
+annualised; it is not a reconstruction of every week's actual award. Supply
+different dates and factual inputs to examine individual assessments. Do not
+interpret the date as a guarantee that policy remains unchanged afterwards.
+
+## Applicable amounts
+
+Child personal allowances use the legacy-benefit child/young-person definition.
+During the historical two-child restriction, actual Child Tax Credit individual
+element counts can permit more children even if the resulting tax-credit payment
+is zero. Continuing-claim protection requires the initial award/count, the
+individual children still in the family, and no subsequent new claim.
+
+The family premium is separate. After its GB or NI abolition date, it requires
+pre-abolition HB entitlement with a child/young person, a continuously qualifying
+family and no new claim. The old higher lone-parent premium requires continuing
+April 1998 statutory protection, not just current lone-parent status.
+
+Disabled-child and enhanced-child premiums require listed disability awards,
+specified hospital suspensions, blindness or the prescribed post-death Child
+Benefit continuation. A general disability indicator is insufficient. These
+premiums are not restricted to the first two child personal allowances. Adult
+premiums remain in the existing shared premium variables; the HB child additions
+do not change Council Tax Reduction or Income Support.
+
+The main-phase ESA age exception tests the claimant personally. A partner's
+main-phase award does not on its own satisfy that exception.
+
+The connected Council Tax Reduction calculation also needs the former
+under-65 pensioner personal allowance. Its category dates are separate from
+HB: England removed it on 6 December 2018, Scotland on 1 February 2021 and
+Wales for schemes from 1 April 2022. Separate referenced CTR rates and Boolean
+schedules preserve those differences. The existing higher-age allowance
+parameters remain shared; HB's new child additions are not imported into CTR.
+The Welsh replacement applies by annual scheme year; it does not change the
+last five days of the model's previous 6-April fiscal year.
+
+## Childcare
+
+Report qualifying charges on each child using
+`housing_benefit_childcare_charges_paid`, with the HB-specific provider category
+and excluded education/partner/relative-care facts. Unknown provider status
+does not establish qualification. The aggregate adult `childcare_expenses`
+input alone does not identify the children or provider and is not substituted
+for these facts.
+
+Work treatment covers actual or expected paid work, specified sickness/credit
+periods after preceding remunerative work, and statutory paid parental leave
+with its relevant end dates. Couples need the corresponding partner work,
+incapacity, inpatient or custody facts. Child age ends on the relevant first
+Monday in September, with actual dates of birth used where supplied.
+
+The capped qualifying charge can offset net earnings after the pre-additional
+earnings disregard, plus actual WTC/CTC income, but not unrelated unearned
+income. The separate pre-additional calculation avoids a circular dependency.
+HB has its own fixed £175/£300 weekly childcare caps, independent of reforms to
+the tax-credit parameters.
+
+## Earnings
+
+The £20 special disregard is not a flat allowance for everyone described as
+disabled or a carer. Working-age and pension-age grounds differ. Specified
+occupation and carer earnings have their own couple aggregation and top-up
+rules. Permitted work requires the actual qualifying benefit/credits, authority
+acceptance, work category, weekly hours and earnings; couples share one limit.
+The higher limit follows the highest adult minimum-wage rate with the statutory
+rounding, not the claimant's age-specific minimum wage.
+
+For savings-credit-only HB, use the Secretary of State's net-income assessment
+and the earnings disregard already included in it. Supply
+`housing_benefit_pension_credit_net_income_assessment` and
+`housing_benefit_pension_credit_earnings_disregard_assessment` together when
+those figures are known. Only permitted HB modifications are deducted: the
+full PC and HB disregards must not both be subtracted.
+
+The fallback reads the model's Pension Credit income. Its disregard adapter
+uses `pension_credit_earnings_disregard` when that separate component is
+installed; otherwise it returns zero, matching the deduction actually made
+by the existing PC-income formula. PR #2019 owns that upstream correction.
+Without it or an actual supplied assessment, the PC estimate retains that
+known limitation. HB does not introduce a second PC calculation.
+
+## Capital
+
+Retained capital is a stock, not annual benefit income. Category amounts must
+already be included in the capital sources being assessed and be disjoint.
+Dates and payment provenance matter: ordinary Carer's Allowance arrears are
+not the July 2026 Independent Review reassessment payment.
+
+The implemented categories cover those reassessment payments, qualifying
+injury payments/trusts, listed benefit arrears and official-error payments,
+specified home/repair funds, business assets and qualifying temporary or
+relative-occupied premises. Working-age 26/52-week rules and pension-age
+calendar-year rules remain distinct. Authority-accepted longer periods must
+be supplied where the provision permits them. These inputs do not represent
+every historic compensation/support scheme listed in the capital schedules.
+
+Remove excluded funds from shared household sources before the claimant/partner
+allocation proxy. Where actual ownership is known, set
+`housing_benefit_owned_household_capital_known` and
+`housing_benefit_owned_household_capital` to the combined claimant/partner
+interest in the configured household sources, excluding separately counted
+LISAs. A known zero replaces the proxy. Remove only those claimants' own
+exclusions in this path. Asset-level ownership and valuation records should
+determine this amount; an equal household-adult share is only a fallback.
+
+The LISA medical exception requires the account manager to have received
+written registered-practitioner evidence of expected life below one year.
+Prospective first-home eligibility alone is not unrestricted surrender:
+the statutory withdrawal is a restricted conveyancer transaction.
+
+## Non-dependants
+
+Normal home elsewhere and youth-training inputs record the exact statutory
+conditions. Income-related ESA under age 25 is exempt only outside the support
+and work-related activity groups; a zero cash component is insufficient.
+Hospital, custody and military-operation exemptions require current absence.
+`housing_benefit_non_dep_linked_inpatient_days` must be prepared from admissions:
+sum inpatient days only, link gaps at most 28 days, and restart after longer
+gaps. Mental-health hospital detention is not the specified custody category.
+
+Full-time students are exempt during study even when working. Working-age
+summer-vacation students are exempt only when not in remunerative work,
+unless the claimant-specific pensionable-age exception applies. NI pension-age
+student rules retain their age-65 condition. Education enrolment is a fallback
+for full-time status; override it for part-time courses.
+
+Pension-age increases use claimant-specific award history. The existing core
+entities cannot store a claimant/non-dependant relationship directly, so
+`housing_benefit_non_dep_increase_history` accepts sparse, validated JSON
+records on each claimant's benefit unit. This is an explicit data interface,
+not an existing standard entity or a generic exemption input:
+
+```json
+[
+  {
+    "person_id": "adult_child",
+    "previous_weekly_deduction": 20.4,
+    "last_effective_date": "2025-04-07",
+    "increases": [
+      {"date": "2026-08-01", "kind": "circumstances"}
+    ]
+  }
+]
+```
+
+Record every pending increase after the current continuous award began or the
+last effective change, whichever is later. Use the amount actually still
+applied before the pending increases, before rent-share allocation. Account
+for ordinary uprating and immediate reductions in that previous amount.
+Event kinds are `arrival`, `circumstances` and `uprating`; only the first two
+start the postponement. Arrival during an existing award normally has a
+previous deduction of zero. An existing resident when a new claim starts
+does not establish a deferred arrival.
+
+The first qualifying increase for the same person determines the 26-week
+date, rounded forward to this claim's benefit-week start. Later increases do
+not restart it. Reductions and exemptions apply immediately. Different
+claimants can supply different histories for the same person. Missing history
+means no evidenced postponement, not a fabricated recent arrival.
+
+## Data and remaining coverage
+
+These factual inputs default to zero/false or an unknown future date. Existing
+datasets are not silently populated with inferred historical awards, payment
+provenance, provider qualifications or claimant-specific change records.
+Population results will use available data and documented fallbacks until
+upstream materialisers supply those fields.
+
+Later pension-age cohort routing, other published rate corrections, general
+non-dependant income/couple rules, within-family deductions, award attribution,
+and more detailed asset valuation are separate model changes. Do not describe
+the model as a complete reconstruction of every HB provision or pre-2015 award.
+
+## Government sources
+
+- [GB working-age HB Regulations](https://www.legislation.gov.uk/uksi/2006/213).
+- [GB pension-age HB Regulations](https://www.legislation.gov.uk/uksi/2006/214).
+- [NI working-age HB Regulations](https://www.legislation.gov.uk/nisr/2006/405).
+- [NI pension-age HB Regulations](https://www.legislation.gov.uk/nisr/2006/406).
+- [Pension Credit earnings disregards](https://www.legislation.gov.uk/uksi/2002/1792/schedule/VI).
+- [2026 GB carers' reassessment exclusion](https://www.legislation.gov.uk/uksi/2026/681).
+- [2026 NI counterpart](https://www.legislation.gov.uk/nisr/2026/146).
+- [LISA medical withdrawal exception](https://www.legislation.gov.uk/uksi/1998/1870/schedule/paragraph/4).
+- [England CTR historical pensioner table](https://www.legislation.gov.uk/uksi/2012/2885/schedule/2/2018-04-01).
+- [Scotland CTR removal of the under-65 category](https://www.legislation.gov.uk/ssi/2020/413/regulation/13/made).
+- [Wales CTR replacement pensioner table](https://www.legislation.gov.uk/wsi/2022/51/regulation/5/made).
+
+The relevant parameters and variables also carry their own source references.

policyengine_uk/parameters/gov/dwp/ESA/permitted_work/former_weeks_limit.yaml

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+description: Former ordinary higher-limit permitted-work duration limit
+values:
+  2015-04-01: 52
+metadata:
+  unit: week
+  label: former ordinary higher-limit permitted-work duration limit
+  reference:
+    - title: Housing Benefit statutory conditions
+      href: https://www.legislation.gov.uk/uksi/2008/794/regulation/45

policyengine_uk/parameters/gov/dwp/ESA/permitted_work/higher_limit_hours.yaml

@@ -0,0 +1,9 @@
+description: Minimum-wage hours used to calculate the higher permitted-work earnings limit
+values:
+  2015-04-01: 16
+metadata:
+  unit: hour
+  label: minimum-wage hours used to calculate the higher permitted-work earnings limit
+  reference:
+    - title: Housing Benefit statutory conditions
+      href: https://www.legislation.gov.uk/uksi/2008/794/regulation/45

policyengine_uk/parameters/gov/dwp/ESA/permitted_work/lower_limit.yaml

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+description: Lower permitted-work weekly earnings limit
+values:
+  2015-04-01: 20
+metadata:
+  unit: currency-GBP
+  label: lower permitted-work weekly earnings limit
+  reference:
+    - title: Housing Benefit statutory conditions
+      href: https://www.legislation.gov.uk/uksi/2008/794/regulation/45

policyengine_uk/parameters/gov/dwp/ESA/permitted_work/ordinary_hours_limit.yaml

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+description: Exclusive weekly hours limit for ordinary higher-limit permitted work
+values:
+  2015-04-01: 16
+metadata:
+  unit: hour
+  label: exclusive weekly hours limit for ordinary higher-limit permitted work
+  reference:
+    - title: Housing Benefit statutory conditions
+      href: https://www.legislation.gov.uk/uksi/2008/794/regulation/45

policyengine_uk/parameters/gov/dwp/ESA/permitted_work/rounding.yaml

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+description: Permitted-work limit upward rounding increment
+values:
+  2015-04-01: 0.5
+metadata:
+  unit: currency-GBP
+  label: permitted-work limit upward rounding increment
+  reference:
+    - title: Housing Benefit statutory conditions
+      href: https://www.legislation.gov.uk/uksi/2008/794/regulation/45

policyengine_uk/parameters/gov/dwp/ESA/permitted_work/weeks_limit_applies.yaml

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+description: Whether the former ordinary higher-limit permitted-work 52-week restriction applies.
+values:
+  2015-04-01: true
+  2017-04-03: false
+metadata:
+  unit: bool
+  label: former permitted-work duration restriction applies
+  reference:
+    - title: Removal of the ESA permitted-work 52-week restriction
+      href: https://www.legislation.gov.uk/uksi/2017/205/regulation/3/made
+    - title: Northern Ireland matching removal from 3 April 2017
+      href: https://www.legislation.gov.uk/nisr/2017/50/regulation/3/made

policyengine_uk/parameters/gov/dwp/housing_benefit/allowances/age_threshold/former_pension_age.yaml

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+description: Age boundary for the former lower pension-age Housing Benefit allowance category.
+values:
+  2015-04-01: 65
+metadata:
+  unit: year
+  label: housing benefit former pension-age allowance boundary
+  reference:
+    - title: Housing Benefit pension-age Regulations 2006, Schedule 3 paragraph 1 as in 2015
+      href: https://www.legislation.gov.uk/uksi/2006/214/schedule/3/2015-04-06

policyengine_uk/parameters/gov/dwp/housing_benefit/allowances/age_threshold/older.yaml

@@ -1,11 +1,15 @@
-description: A higher Houseing Benefit allowance amount is provided for filers over this age threshold.
+description: >-
+  Inclusive age threshold for a single claimant's higher working-age Housing
+  Benefit personal allowance, subject to statutory exceptions.
 metadata:
   label: Housing benefit allowance older age threshold
   period: year
   unit: year
-  reference: 
-    - title: The Housing Benefit Regulations 2006 sec. 74
-      href: https://www.legislation.gov.uk/uksi/2006/213/made/data.pdf#page=73
+  reference:
+    - title: The Housing Benefit Regulations 2006 Schedule 3 Part 1 paragraph 1, as made
+      href: https://www.legislation.gov.uk/uksi/2006/213/schedule/3/part/1/made
+    - title: The Housing Benefit Regulations (Northern Ireland) 2006 Schedule 4 Part I paragraph 1
+      href: https://www.legislation.gov.uk/nisr/2006/405/schedule/4
 
 values:
   2019-04-01: 25

policyengine_uk/parameters/gov/dwp/housing_benefit/allowances/age_threshold/younger.yaml

@@ -1,11 +1,16 @@
-description: A lower Housing Benefit allowance amount is provided if both members of a couple are below this age threshold.
+description: >-
+  Inclusive age threshold for the higher working-age Housing Benefit personal
+  allowance for a lone parent or a couple with at least one member at this age,
+  subject to statutory exceptions.
 metadata:
   label: Housing benefit allowance younger age threshold
   period: year
   unit: year
-  reference: 
-    - title: The Housing Benefit Regulations 2006 sec. 74
-      href: https://www.legislation.gov.uk/uksi/2006/213/made/data.pdf#page=73
+  reference:
+    - title: The Housing Benefit Regulations 2006 Schedule 3 Part 1 paragraph 1, as made
+      href: https://www.legislation.gov.uk/uksi/2006/213/schedule/3/part/1/made
+    - title: The Housing Benefit Regulations (Northern Ireland) 2006 Schedule 4 Part I paragraph 1
+      href: https://www.legislation.gov.uk/nisr/2006/405/schedule/4
 
 values:
   2019-04-01: 18

policyengine_uk/parameters/gov/dwp/housing_benefit/allowances/child.yaml

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+description: Weekly Housing Benefit personal allowance for each qualifying child or young person, distinct from premiums.
+values:
+  2015-04-01: 66.9
+  2020-04-01: 68.27
+  2021-04-01: 68.6
+  2022-04-01: 70.8
+  2023-04-01: 77.78
+  2024-04-01: 83.24
+  2025-04-01: 84.66
+  2026-04-01: 87.88
+metadata:
+  unit: currency-GBP
+  label: housing benefit child personal allowance
+  period: week
+  uprating: gov.benefit_uprating_cpi
+  reference:
+    - title: Housing Benefit statutory rule 1
+      href: https://www.legislation.gov.uk/uksi/2006/213/schedule/3/paragraph/2
+    - title: Housing Benefit statutory rule 2
+      href: https://www.legislation.gov.uk/uksi/2015/457/article/18/made
+    - title: Housing Benefit statutory rule 3
+      href: https://www.legislation.gov.uk/uksi/2020/234/article/24/made
+    - title: Housing Benefit statutory rule 4
+      href: https://www.legislation.gov.uk/uksi/2021/162/article/24/made
+    - title: Housing Benefit statutory rule 5
+      href: https://www.legislation.gov.uk/uksi/2022/292/article/24/made
+    - title: Housing Benefit statutory rule 6
+      href: https://www.legislation.gov.uk/uksi/2023/316/article/24/made
+    - title: Housing Benefit statutory rule 7
+      href: https://www.legislation.gov.uk/uksi/2024/242/article/23/made
+    - title: Housing Benefit statutory rule 8
+      href: https://www.legislation.gov.uk/uksi/2025/295/article/23/made
+    - title: Housing Benefit statutory rule 9
+      href: https://www.legislation.gov.uk/uksi/2026/148/article/23/made

policyengine_uk/parameters/gov/dwp/housing_benefit/allowances/child_limit/count.yaml

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+description: Ordinary maximum number of child personal allowances while the Housing Benefit child restriction applies.
+values:
+  2015-04-01: 2
+metadata:
+  unit: child
+  label: housing benefit ordinary child allowance limit
+  reference:
+    - title: Housing Benefit statutory rule 1
+      href: https://www.legislation.gov.uk/uksi/2017/376/made
+    - title: Housing Benefit statutory rule 2
+      href: https://www.legislation.gov.uk/nisr/2017/79/made
+    - title: Housing Benefit statutory rule 3
+      href: https://www.legislation.gov.uk/uksi/2024/611/regulation/6
+    - title: Housing Benefit statutory rule 4
+      href: https://www.legislation.gov.uk/nisr/2024/119/regulation/5
+    - title: Housing Benefit statutory rule 5
+      href: https://www.legislation.gov.uk/uksi/2026/316/regulation/2
+    - title: Housing Benefit statutory rule 6
+      href: https://www.legislation.gov.uk/nisr/2026/68/regulation/2