Give Universal Credit and Housing Benefit their own benefit cap and LHA shared-accommodation rules

changelog.d/uc-hb-split-shared-cap-lha-rules.added.md

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+Per-scheme benefit cap variables (`uc_benefit_cap`, `is_uc_benefit_cap_single_claimant_rate`, `is_uc_benefit_cap_exempt`, `is_uc_benefit_cap_exempt_earnings`, `is_uc_benefit_cap_exempt_specified_benefit`, `is_uc_benefit_cap_exempt_qualifying_age`, `uc_benefit_cap_reduction`; `housing_benefit_benefit_cap`, `is_housing_benefit_benefit_cap_single_claimant_rate`, `is_housing_benefit_benefit_cap_exempt`, `is_housing_benefit_benefit_cap_exempt_working_tax_credit`, `is_housing_benefit_benefit_cap_exempt_specified_benefit`, `housing_benefit_benefit_cap_reduction`; `benefit_cap_welfare_benefits`), with the parameter `gov.dwp.housing_benefit.minimum_weekly_amount`.

changelog.d/uc-hb-split-shared-cap-lha-rules.fixed.md

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+Universal Credit and Housing Benefit each apply their own benefit cap. The UC cap (UC Regs 2013 regs 79-83) treats a member of a couple claiming as a single person (reg 3(3)) as a single claimant, lifts the cap for earnings and the LCWRA and carer elements but not for working tax credit, lifts it on age only where the single claimant or both joint claimants have reached the qualifying age for State Pension Credit (SI 2014/1230 reg 60C), and takes the childcare costs element off the reduction (reg 81). The HB cap (HB Regs 2006 Part 8A) treats that couple as a couple, lifts the cap for working tax credit and the benefits in reg 75F (the partner's included) but not for earnings or UC elements, does not reach pension-age claims (reg 5), and leaves at least 50 pence a week of HB (reg 75D(2)). The UC shared accommodation test (`is_lha_shared_accommodation_rate_specified_renter`, UC Sch 4 paras 27-29) applies reg 3(3) whatever legacy benefits the family reports, and armed forces independence payment now excepts a renter under 35 from it (UC reg 2) and lifts both caps (UC reg 83(1)(c) with reg 2; HB reg 75F(1)(ea)). The `claims_legacy_benefits` stopgap for reg 3(3) single claims is gone.

changelog.d/uc-hb-split-shared-cap-lha-rules.removed.md

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+The shared benefit cap variables `benefit_cap`, `is_benefit_cap_exempt`, `is_benefit_cap_exempt_earnings`, `is_benefit_cap_exempt_health_disability`, `is_benefit_cap_exempt_other` and `is_benefit_cap_single_claimant_rate`, replaced by each scheme's own. `benefit_cap_reduction` remains as the sum of the Universal Credit and Housing Benefit reductions.

docs/book/programs/gov/dwp/housing-benefit.ipynb

@@ -40,11 +40,11 @@
     "\n",
     "The award is computed in four stages:\n",
     "\n",
-    "1. **Eligible rent**: the rent the benunit is liable for (`benunit_rent`). Where the Local Housing Allowance applies (`LHA_eligible`: renting, and no member in social housing), the eligible rent is the maximum rent (LHA), which is the LHA rate or, where the rent is lower, the rent (`LHA_cap`; SI 2006/213 regs [12D(2)(a)](https://www.legislation.gov.uk/uksi/2006/213/regulation/12D) and [13D(5)](https://www.legislation.gov.uk/uksi/2006/213/regulation/13D)).\n",
+    "1. **Eligible rent**: the rent the benunit is liable for (`benunit_rent`). Where the Local Housing Allowance applies (`LHA_eligible`: renting, and no member in social housing), the eligible rent is the maximum rent (LHA), which is the LHA rate for the Housing Benefit category of dwelling (`housing_benefit_LHA_category`: the shared accommodation rate for a young individual with no non-dependant, or a claimant entitled to one bedroom who lacks exclusive use of self-contained accommodation, unless the severe disability premium applies, reg 13D(2)) or, where the rent is lower, the rent (`LHA_cap`; SI 2006/213 regs [12D(2)(a)](https://www.legislation.gov.uk/uksi/2006/213/regulation/12D) and [13D(5)](https://www.legislation.gov.uk/uksi/2006/213/regulation/13D)).\n",
     "2. **Applicable amount** (`housing_benefit_applicable_amount`): a personal allowance derived from the benunit's composition (single, couple, lone parent) and age, plus any disability/carer premiums. This is the \"minimum income\" the household needs before HB tapers begin.\n",
     "3. **Means test** (`housing_benefit_entitlement`): the appropriate maximum Housing Benefit is the eligible rent less `housing_benefit_non_dep_deductions` for any non-dependant adults living in the household ([reg. 70](https://www.legislation.gov.uk/uksi/2006/213/regulation/70)). The published `withdrawal_rate` (currently 0.65) of the benunit's `housing_benefit_applicable_income` in excess of the applicable amount is deducted from that maximum ([SSCBA 1992 s. 130(3)(b)](https://www.legislation.gov.uk/ukpga/1992/4/section/130), [reg. 71](https://www.legislation.gov.uk/uksi/2006/213/regulation/71)). Because the LHA caps the eligible rent, the taper comes off the LHA: a private tenant with rent above the LHA and income above the applicable amount receives the LHA less the taper, not the lower of the LHA and the rent less the taper. The pension-age regulations (SI 2006/214) have the same rules at regs 12D, 13D, 50 and 51, and the Northern Ireland regulations at SR 2006/405 regs 13C, 14D, 68 and 69 and SR 2006/406 regs 13C, 14D, 48 and 49.\n",
     "   If the claimant or partner is on Universal Credit, Income Support, income-based Jobseeker's Allowance or income-related Employment and Support Allowance (`housing_benefit_on_passporting_benefit`), the whole of the family's earnings, other income and capital is disregarded ([SI 2006/213 Sch. 4 para. 12](https://www.legislation.gov.uk/uksi/2006/213/schedule/4/paragraph/12), [Sch. 5 para. 4](https://www.legislation.gov.uk/uksi/2006/213/schedule/5/paragraph/4) and [Sch. 6 para. 5](https://www.legislation.gov.uk/uksi/2006/213/schedule/6/paragraph/5); Northern Ireland: [SR 2006/405 Sch. 5 para. 12](https://www.legislation.gov.uk/nisr/2006/405/schedule/5/paragraph/12), [Sch. 6 para. 4](https://www.legislation.gov.uk/nisr/2006/405/schedule/6/paragraph/4) and [Sch. 7 para. 5](https://www.legislation.gov.uk/nisr/2006/405/schedule/7/paragraph/5)). `housing_benefit_applicable_income` and `housing_benefit_assessable_capital` are then zero, so the award is that maximum. This applies at any age: a mixed-age couple whose younger member is on one of these benefits is assessed under the working-age regulations ([SI 2006/213 reg. 5(1)(b)](https://www.legislation.gov.uk/uksi/2006/213/regulation/5)). Income Support, income-based Jobseeker's Allowance and income-related Employment and Support Allowance count when a positive amount is paid on the claimant's or partner's award (`in_receipt_of_income_support_jsa_ib_or_esa_ir`, which reads `claimant_or_partner_jsa_income` and `claimant_or_partner_esa_income`). Another member's own award, such as a non-dependant's, is payable to them and does not passport the claimant. A person is on Universal Credit on any day they are entitled to it, whether it is in payment or not ([reg. 2(3B)](https://www.legislation.gov.uk/uksi/2006/213/regulation/2)); PolicyEngine reads that as Universal Credit above nil before the benefit cap and deductions (`is_uc_entitled`), for a family that claims it, so the passport adds no circular dependency through the benefit cap. The universal credit limb applies from 28 October 2013 in Great Britain and 8 May 2018 in Northern Ireland (`gov.dwp.housing_benefit.means_test.universal_credit_passport`). It matters only where Housing Benefit is paid alongside Universal Credit, for specified or temporary accommodation, which the eligibility rules above do not yet model.\n",
-    "4. **Benefit cap** (`housing_benefit`): the post-means-test award is finally reduced by `benefit_cap_reduction` if the household's total benefit income exceeds the cap and no cap exemption applies.\n",
+    "4. **Benefit cap** (`housing_benefit`): the post-means-test award is finally reduced by `housing_benefit_benefit_cap_reduction`, the excess of the family's welfare benefits over the Housing Benefit cap (`housing_benefit_benefit_cap`, SI 2006/213 reg 75CA), leaving at least 50 pence a week (reg 75D). The cap does not apply where the claimant or couple is entitled to working tax credit (reg 75E), the claimant or partner receives a benefit listed in reg 75F, or the claim is under the pension-age regulations (reg 5). Universal Credit has its own cap.\n",
     "\n",
     "The take-up gate (`would_claim_housing_benefit`) is applied inside `housing_benefit_pre_benefit_cap`."
    ]

docs/book/programs/gov/dwp/universal-credit.ipynb

@@ -44,7 +44,7 @@
   {
    "cell_type": "markdown",
    "metadata": {},
-   "source": "## How PolicyEngine computes Universal Credit\n\nPolicyEngine computes Universal Credit at the benefit-unit level in three stages:\n\n1. **Maximum entitlement** (`uc_maximum_amount`): sum the elements the benunit qualifies for — `uc_standard_allowance`, `uc_child_element`, `uc_disability_elements`, `uc_carer_element`, `uc_housing_costs_element`, and `uc_childcare_element`.\n2. **Means test**: only the claimants' income counts: the single claimant, or the two joint claimants (`is_uc_assessed_claimant`; UC Regulations 2013 reg 22(1)). The earnings and unearned income of a child, a qualifying young person or anyone else in the benefit unit are theirs, not the claimant's, so the Universal Credit means test does not count them. Who the claimants are comes from `is_uc_claimant` (the claimant and partner); a member flagged there is taken as a claimant whatever their age. Each person's earnings (`uc_individual_earned_income`) are net of their own relievable pension contributions and the income tax and National Insurance they pay on that employment or self-employment (UC Regulations 2013 regs 55(5) and 57(2)): `uc_income_tax_on_earnings` treats earnings as the lowest slice of the person's non-savings income, so tax on pensions, property, savings and dividends is never deducted, and one partner's tax never reduces the other's earnings. A claimant in gainful self-employment outside a start-up period who would otherwise be subject to all work-related requirements is subject to the minimum income floor (reg 62): when their earnings after those deductions are below `uc_minimum_income_floor`, they are treated as having that amount instead. The floor does not apply to a claimant in the no work-related requirements, work-focused interview or work preparation group (`uc_work_related_group_apart_from_earnings`; Welfare Reform Act 2012 ss 19 to 21): for example one with limited capability for work-related activity, a carer, a claimant over State Pension Credit qualifying age, or the responsible carer of a child under 3. Only one member of a couple is the responsible carer (`uc_is_responsible_carer`); where the nomination is not supplied the model takes the claimant who works fewer hours (`hours_worked`), then the elder. `hours_worked` defaults to 0, so for a couple entered without hours the default falls to the elder; supply `uc_is_responsible_carer` where the nomination is known. The floor is the minimum wage for their age for their expected hours (`uc_expected_hours`: 35 a week, or for the responsible carer of a child under 13 the hours DWP uses: 30 from February 2025, from April 2017 until then 16 for a child under compulsory school age and 25 for an older child, and 25 for any child under 13 before April 2017; regs 88 and 90(2)), less the income tax and the Class 2 and Class 4 National Insurance a self-employed person would pay on it (reg 62(4)(b) leaves this amount to the Secretary of State; this is the basis of DWP's guidance and figures, and setting the `gov.dwp.universal_credit.means_test.minimum_income_floor.self_employed_national_insurance` parameter to false deducts primary Class 1 instead). A member of a couple is lifted only while the couple's combined earnings are below the couple threshold, and never above it (reg 62(3)). The couple threshold is the sum of both partners' thresholds (reg 90(3)): 16 hours for a partner in the work-focused interview or work preparation group, nothing for a partner with no work-related requirements for a reason other than earnings, and 35 hours at the national living wage (the adult rate before April 2016) for a partner who cannot be a joint claimant (reg 90(3)(b)). The maximum entitlement is then reduced by 55% (the `gov.dwp.universal_credit.means_test.reduction_rate` parameter) of the claimants' combined earnings above the work allowance (`uc_work_allowance`), and by all of the claimants' unearned income (`uc_unearned_income`), pound for pound. Unearned income is the list in `gov.dwp.universal_credit.means_test.income_definitions.unearned`: retirement pension income (State Pension and private pensions, UC Regulations 2013 regs 66(1)(a) and 67), Carer's Allowance, carer support payment (up to the Carer's Allowance rate, from November 2023), contribution-based JSA and ESA, maternity allowance, industrial injuries benefit, and the tariff income deemed from capital (reg 72). Actual savings interest, dividends and ordinary rental income are excluded from UC unearned income at every capital level; capital counts through its tariff income instead. Asset rules apply on top of this — capital above the lower threshold deems a tariff income, and capital above the upper threshold disqualifies the benunit entirely.\n3. **Benefit cap**: the post-means-test award (`universal_credit_pre_benefit_cap`) is finally reduced by `benefit_cap_reduction` to produce `universal_credit`. The benefit cap only applies to benunits without a benefit-cap exemption (the claimants earning enough, having a qualifying disability benefit, etc.). The earnings exception reads the claimants' earnings only (reg 82(1)(a)), the capped total counts only the claimants' own contributory benefits (WRA 2012 s.96(1)), and the childcare work condition tests only the claimants (reg 32(1)).\n\nThe take-up step is handled by the input variable `would_claim_uc`, which is populated stochastically when the dataset is built so that PolicyEngine's caseload aggregates match published DWP claimant numbers rather than the full eligible population.\n\nParameters live in `policyengine_uk/parameters/gov/dwp/universal_credit/` and the per-element formulas in `policyengine_uk/variables/gov/dwp/universal_credit/`."
+   "source": "## How PolicyEngine computes Universal Credit\n\nPolicyEngine computes Universal Credit at the benefit-unit level in three stages:\n\n1. **Maximum entitlement** (`uc_maximum_amount`): sum the elements the benunit qualifies for — `uc_standard_allowance`, `uc_child_element`, `uc_disability_elements`, `uc_carer_element`, `uc_housing_costs_element`, and `uc_childcare_element`.\n2. **Means test**: only the claimants' income counts: the single claimant, or the two joint claimants (`is_uc_assessed_claimant`; UC Regulations 2013 reg 22(1)). The earnings and unearned income of a child, a qualifying young person or anyone else in the benefit unit are theirs, not the claimant's, so the Universal Credit means test does not count them. Who the claimants are comes from `is_uc_claimant` (the claimant and partner); a member flagged there is taken as a claimant whatever their age. Each person's earnings (`uc_individual_earned_income`) are net of their own relievable pension contributions and the income tax and National Insurance they pay on that employment or self-employment (UC Regulations 2013 regs 55(5) and 57(2)): `uc_income_tax_on_earnings` treats earnings as the lowest slice of the person's non-savings income, so tax on pensions, property, savings and dividends is never deducted, and one partner's tax never reduces the other's earnings. A claimant in gainful self-employment outside a start-up period who would otherwise be subject to all work-related requirements is subject to the minimum income floor (reg 62): when their earnings after those deductions are below `uc_minimum_income_floor`, they are treated as having that amount instead. The floor does not apply to a claimant in the no work-related requirements, work-focused interview or work preparation group (`uc_work_related_group_apart_from_earnings`; Welfare Reform Act 2012 ss 19 to 21): for example one with limited capability for work-related activity, a carer, a claimant over State Pension Credit qualifying age, or the responsible carer of a child under 3. Only one member of a couple is the responsible carer (`uc_is_responsible_carer`); where the nomination is not supplied the model takes the claimant who works fewer hours (`hours_worked`), then the elder. `hours_worked` defaults to 0, so for a couple entered without hours the default falls to the elder; supply `uc_is_responsible_carer` where the nomination is known. The floor is the minimum wage for their age for their expected hours (`uc_expected_hours`: 35 a week, or for the responsible carer of a child under 13 the hours DWP uses: 30 from February 2025, from April 2017 until then 16 for a child under compulsory school age and 25 for an older child, and 25 for any child under 13 before April 2017; regs 88 and 90(2)), less the income tax and the Class 2 and Class 4 National Insurance a self-employed person would pay on it (reg 62(4)(b) leaves this amount to the Secretary of State; this is the basis of DWP's guidance and figures, and setting the `gov.dwp.universal_credit.means_test.minimum_income_floor.self_employed_national_insurance` parameter to false deducts primary Class 1 instead). A member of a couple is lifted only while the couple's combined earnings are below the couple threshold, and never above it (reg 62(3)). The couple threshold is the sum of both partners' thresholds (reg 90(3)): 16 hours for a partner in the work-focused interview or work preparation group, nothing for a partner with no work-related requirements for a reason other than earnings, and 35 hours at the national living wage (the adult rate before April 2016) for a partner who cannot be a joint claimant (reg 90(3)(b)). The maximum entitlement is then reduced by 55% (the `gov.dwp.universal_credit.means_test.reduction_rate` parameter) of the claimants' combined earnings above the work allowance (`uc_work_allowance`), and by all of the claimants' unearned income (`uc_unearned_income`), pound for pound. Unearned income is the list in `gov.dwp.universal_credit.means_test.income_definitions.unearned`: retirement pension income (State Pension and private pensions, UC Regulations 2013 regs 66(1)(a) and 67), Carer's Allowance, carer support payment (up to the Carer's Allowance rate, from November 2023), contribution-based JSA and ESA, maternity allowance, industrial injuries benefit, and the tariff income deemed from capital (reg 72). Actual savings interest, dividends and ordinary rental income are excluded from UC unearned income at every capital level; capital counts through its tariff income instead. Asset rules apply on top of this — capital above the lower threshold deems a tariff income, and capital above the upper threshold disqualifies the benunit entirely.\n3. **Benefit cap**: the post-means-test award (`universal_credit_pre_benefit_cap`) is finally reduced by `uc_benefit_cap_reduction` to produce `universal_credit`: the excess of the family's welfare benefits over the Universal Credit cap (`uc_benefit_cap`, UC Regulations 2013 reg 80A), less the childcare costs element (reg 81). The cap does not apply where earnings reach the reg 82 threshold or a claimant receives a benefit or element listed in reg 83 (`is_uc_benefit_cap_exempt`). A member of a couple claiming as a single person (reg 3(3)) has the single-claimant limit. The earnings exception reads the claimants' earnings only (reg 82(1)(a)), the capped total counts only the claimants' own contributory benefits (WRA 2012 s.96(1)), and the childcare work condition tests only the claimants (reg 32(1)). Housing Benefit has its own cap.\n\nThe take-up step is handled by the input variable `would_claim_uc`, which is populated stochastically when the dataset is built so that PolicyEngine's caseload aggregates match published DWP claimant numbers rather than the full eligible population.\n\nParameters live in `policyengine_uk/parameters/gov/dwp/universal_credit/` and the per-element formulas in `policyengine_uk/variables/gov/dwp/universal_credit/`."
   },
   {
    "cell_type": "code",