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

[MaxGhenis]

Stacked on #2084 (UC reg 3(3) single claims; base branch uc-reg3-3-single-claim). Review the commits after 17b9b8a16; the head is c8fd1c9. GitHub retargets this PR to main when #2084 merges.

What was wrong

One set of variables served both Universal Credit and Housing Benefit although the two schemes' rules differ:

• Cap rate. is_benefit_cap_single_claimant_rate / benefit_cap used one "single claimant" test. UC Regs 2013 reg 80A(2) and HB Regs 2006 reg 75CA(2) each define it their own way.
• Cap exceptions. is_benefit_cap_exempt_health_disability, _other and _earnings were the union of both schemes' grounds:
  • UC's earnings exception and LCWRA and carer elements also lifted the HB cap.
  • HB's working tax credit exception also lifted the UC cap.
  • Any member over State Pension age lifted both caps. UC has no age exception, and HB's cap is out of reach only under the pension-age regulations.
• Cap reduction. benefit_cap_reduction served both, and applied neither UC reg 81 (the childcare costs element comes off) nor HB reg 75D(2) (the 50p weekly minimum stays).
• LHA shared accommodation rate. is_lha_shared_accommodation_rate_specified_renter set the one category both schemes read. UC Sch 4 paras 27-29 and HB reg 2(1) "young individual" with reg 13D(2)(a)(i) differ: UC has a single claim by a member of a couple and HB does not.

#2084 gated the reg 3(3) consequences in these shared variables on claims_legacy_benefits as a stopgap. That stopgap was wrong for any family whose legacy status did not match the scheme being calculated.

The law

legislation.gov.uk data.xml, current text, fetched 2026-10-02.

Who is a single claimant

• UC reg 3(3): "A person who is a member of a couple may make a claim as a single person if the other member of the couple— (a) does not meet the basic condition in section 4(1)(a) (at least 18 years old) and is not a person in respect of whom the minimum age specified in regulation 8 applies; ..."
• UC reg 78(2): "In this Part 'couple' means— (a) joint claimants; or (b) a single claimant who is a member of a couple within the meaning of section 39 of the Act and the other member of that couple".
• UC reg 80A(2): "(a) £16,967 for a single claimant resident in Greater London who is not responsible for a child or qualifying young person; (b) £25,323 for— (i) joint claimants where either joint claimant is resident in Greater London; (ii) a single claimant resident in Greater London who is responsible for a child or qualifying young person; (c) £14,753 for a single claimant not resident in Greater London who is not responsible for a child or qualifying young person; (d) £22,020 for— (i) joint claimants not resident in Greater London; (ii) a single claimant not resident in Greater London who is responsible for a child or qualifying young person."
• HB reg 75CA(2): "(a) £16,967 in the case of single claimants resident in Greater London; (b) £25,323 in the case of all other claimants resident in Greater London; (c) £14,753 in the case of single claimants not resident in Greater London; (d) £22,020 in the case of all other claimants not resident in Greater London."
• HB reg 2(1): "'single claimant' means a claimant who neither has a partner nor is a lone parent"; "'lone parent' means a person who has no partner and who is responsible for and a member of the same household as a child or young person".

Exceptions

• UC reg 79(1): "Unless regulation 82 or 83 applies, the benefit cap applies where the welfare benefits to which a single person or couple is entitled during the reference period exceed the relevant amount".
• UC reg 82(1)(a): "the claimant's earned income or, if the claimant is a member of a couple, the couple's combined earned income, is equal to or exceeds [16 hours at the national minimum wage, monthly]".
• UC reg 83(1): "(a) the LCWRA element is included in the award of universal credit or the claimant is receiving an employment and support allowance that includes the support component; (b) a claimant is receiving industrial injuries benefit; (c) a claimant is receiving attendance allowance; ... (g) a claimant, or a qualifying young person for whom a claimant is responsible, is receiving personal independence payment; ... (i) a claimant, or a qualifying young person for whom a claimant is responsible, is entitled to carer's allowance; ... (j) the carer element is included in the award of universal credit".
• HB reg 75A: "Unless regulation 75E or 75F applies, a benefit cap applies ...".
• HB reg 75E(2): "This paragraph applies where the claimant is, or the claimant and the claimant's partner are jointly, entitled to working tax credit."
• HB reg 75F(1): "(a) the claimant or the claimant's partner is receiving an employment and support allowance ... which includes a support component; (b) the claimant or the claimant's partner is receiving an industrial injuries benefit ...; (c) ... attendance allowance; ... (ea) the claimant, the claimant's partner or a young person for whom the claimant or the claimant's partner is responsible, is receiving a personal independence payment ...; ... (h) ... is entitled to a carer's allowance".
• HB reg 5: "(1) These Regulations apply to a person who— (a) has not attained the qualifying age for state pension credit; or (b) has attained the qualifying age for state pension credit if he, or if he has a partner, his partner, is a person on universal credit, on income support, on an income-based jobseeker's allowance or on an income-related employment and support allowance. ... (3) Except as provided in paragraph (1), these Regulations shall not apply in relation to any person if he, or if he has a partner, his partner, has attained the qualifying age for state pension credit." The benefit cap is Part 8A of these Regulations. The pension-age regulations (SI 2006/214) have no cap. The pension-age carve-out is reg 5, not reg 75C; reg 75C sets how each welfare benefit is counted.

Reductions

• UC reg 81: "(1) ... the amount of the award for that period is to be reduced by— (a) the excess; minus (b) any amount included in the award for the childcare costs element in relation to that assessment period. (2) But no reduction is to be applied where the amount of the childcare costs element is greater than the excess."
• HB reg 75D(2): "Where the reduction would reduce the claimant's housing benefit to less than the minimum amount of housing benefit provided for in regulation 75 (minimum housing benefit), the relevant authority must reduce the claimant's housing benefit by such amount as will leave the claimant entitled to that minimum amount." Reg 75: "... it shall not be payable where the amount to which a person would otherwise be entitled is less than 50 pence per benefit week."

Shared accommodation

• UC Sch 4 para 28: "(2) The first condition is that the renter is a single person (or a member of a couple claiming as a single person) who— (a) is under 35 years old; and (b) is not an excepted person under paragraph 29. (3) The second condition is that the renter is not responsible for any children or qualifying young persons. (4) The third condition is that no person is a non-dependant in relation to the renter."
• UC Sch 4 para 29(5): "E is under 35 years old and is in receipt of— (a) the care component of disability living allowance at the middle or highest rate; ... (b) attendance allowance; ... (c) the daily living component of personal independence payment". UC reg 2: "'attendance allowance' means— ... armed forces independence payment under the Armed Forces and Reserve Forces (Compensation Scheme) Order 2011".
• HB reg 13D(2)(a): "(i) the claimant is a young individual who has no non-dependant residing with him and to whom paragraph 14 of Schedule 3 (severe disability premium) does not apply". HB reg 2(1): "'young individual' means a single claimant who has not attained the age of 35 years, but does not include such a claimant— [care leavers, overnight care, hostels, MAPPA, a qualifying parent or carer, domestic violence, modern slavery ...]".
• HB Sch 3 para 14(2)(a): "(i) he is in receipt of attendance allowance, the care component of disability living allowance at the highest or middle rate ..., the daily living component of personal independence payment ... or armed forces independence payment; and (ii) ... he has no non-dependants aged 18 or over normally residing with him ...; and (iii) no person is entitled to, and in receipt of, a carer's allowance ... in respect of caring for him".

So Housing Benefit's counterpart to UC's para 29(5) disability exception is the severe disability premium condition. In the model both lists come to the same benefits: attendance allowance, DLA care at the middle or highest rate, PIP daily living and AFIP. Para 14's carer condition (iii) is not observed.

What this PR does

	Universal Credit	Housing Benefit
Cap	uc_benefit_cap (reg 80A)	housing_benefit_benefit_cap (reg 75CA)
Single-claimant rate	is_uc_benefit_cap_single_claimant_rate: not joint claimants (a reg 3(3) single claim is single), not responsible for a child or QYP	is_housing_benefit_benefit_cap_single_claimant_rate: is_single_person (reg 2(1)); a reg 3(3) couple is a couple
Exceptions	is_uc_benefit_cap_exempt = _earnings (reg 82) or _specified_benefit (reg 83: LCWRA and carer elements, a claimant's benefits including armed forces independence payment as attendance allowance (reg 2); the reg 3(3) other member is not a claimant). No WTC, no age exception.	is_housing_benefit_benefit_cap_exempt = _working_tax_credit (75E) or _specified_benefit (75F, AFIP included; the partner's benefits count) or housing_benefit_pension_age_regulations_apply (reg 5). No earnings, LCWRA or carer-element exception.
Reduction	uc_benefit_cap_reduction: excess less the childcare costs element, on an award only (regs 78(1), 81)	housing_benefit_benefit_cap_reduction: excess, leaving 50p a week (regs 75, 75D)
Award reads	universal_credit, uc_deductions, uc_has_deduction	housing_benefit
LHA category	LHA_category with is_lha_shared_accommodation_rate_specified_renter (Sch 4 paras 27-29; reg 3(3) without the stopgap; AFIP added per reg 2)	housing_benefit_LHA_category with is_housing_benefit_young_individual and housing_benefit_severe_disability_premium_applies (reg 13D(2)(a)(i), Sch 3 para 14)
LHA rate	uc_LHA_cap (unchanged)	LHA_cap now reads housing_benefit_LHA_rate

Other changes:

• benefit_cap_welfare_benefits is the welfare benefits total. The model pays a family UC or HB, never both, so one total serves both schemes; a property test checks that no family has both. UC reg 80(2A), which counts HB as nil, and HB reg 75F(1)(g), which exempts a claimant receiving UC, therefore never bind.
• benefit_cap_reduction remains, as the sum of the two schemes' reductions. Downstream code reads it: uk-data's DWP benefit-cap calibration targets do. A family with neither award now has no reduction; in the Enhanced FRS no family had a reduction without an award, so that gate moves nothing. The calibration targets are for 2025, where the count of capped benefit units is identical and the reduction total matches to floating-point noise. From 2026 the total falls by reg 81's childcare offset (£0.14m in 2026, £1.39m in 2030). The UC part is the reg 81 amount, which can exceed the award before the cap (universal_credit floors the award at nil). That predates this PR; bounding the reported amount changes uk-data's monetary inputs, so it is a follow-up.
• The claims_legacy_benefits stopgap helpers in utils/uc_work_related_requirements.py are gone.
• Removed: benefit_cap, is_benefit_cap_exempt, is_benefit_cap_exempt_earnings, is_benefit_cap_exempt_health_disability, is_benefit_cap_exempt_other, is_benefit_cap_single_claimant_rate. The program registry (programs.yaml, served at /uk/metadata) now names benefit_cap_reduction for the Benefit Cap. Four other registry entries were already broken before this PR (JSA, ESA, DLA, winter_fuel_payment); they are a separate follow-up with a registry test.

Converging with #2006/#2030. The LHA names come from #2006 so the two branches meet on the same files: housing_benefit_LHA_category, housing_benefit_LHA_rate, is_housing_benefit_young_individual, housing_benefit_severe_disability_premium_applies, the parameter gov.dwp.housing_benefit.severe_disability_premium.qualifying_benefits, lha_rate_for_category and category_maximum(..., category_variable). In #2006, LHA_category stays the UC category. Where #2006 has more (the reg 13D(2)(a)(ii) route, sharers' rent, its own non-dependant tests), its versions supersede these. This PR keeps today's household-composition proxy (lha_renter_has_non_dependant) for both schemes. Both shared-rate tests still read responsibility under either scheme: a dependant under one scheme only is the other scheme's non-dependant, which the proxy does not identify. #2030 replaces both with each scheme's own non-dependant test.

Not modelled (as before): the UC grace period (reg 82(1)(b)), the HB 39-week grace period (75E(3)-(5)), the weekly rounding of HB's relevant amount (75CA(1)), the reg 75 non-payment of HB below 50p, the para 29 / reg 2(1) exceptions other than disability benefits, and Sch 3 para 14(2)(a)(iii).

Impact

Real Enhanced FRS runs, one at a time. Base is #2084's head 17b9b8a. Branch is c8fd1c9 (run r2, after the AFIP cap exception); run r1 at bd9a5a7 gave identical numbers. Private copy of enhanced_frs_2024_25.h5, sha256 e433e532…. Weighted £m a year; records are survey records.

Year	UC	HB	Household net income	UC benefit units changed	of which reg 81 childcare offset (records)	UC families capped, base → branch	HB families capped (base)	UC exemption lost (records)	HB exemption lost	LHA category changed (UC/HB vs UC)	AHC poverty (pp)
2025	+0.00	+0.00	+0.00	0	0	133k → 133k	0	8 (3.5k)	0	0/0	0.0000
2026	+0.14	+0.00	+0.14	2 records (0.6k)	2	267k → 267k	0	8 (3.6k)	0	0/0	0.0000
2027	+0.14	+0.00	+0.14	2 (0.6k)	2	303k → 303k	0	8 (3.6k)	0	0/0	0.0000
2028	+0.14	+0.00	+0.14	2 (0.6k)	2	341k → 341k	0	8 (3.6k)	0	0/0	0.0000
2029	+0.15	+0.00	+0.15	2 (0.6k)	2	358k → 358k	0	8 (3.6k)	0	0/0	0.0000
2030	+1.39	+0.00	+1.39	6 (15.5k)	6	396k → 381k	0	8 (3.6k)	0	0/0	0.0000

• Every UC change is reg 81's childcare costs element.
• The UC exemption losses (8 records, about 3.6k benefit units) are mixed-age couples on UC. Under the old shared rule any member at State Pension age exempted them. None is above the cap, so £0; this matches Apply the benefit cap to mixed-age couples on Universal Credit, and keep them off pensioner Council Tax Reduction #1944's finding.
• HB: no HB family in the EFRS is above the cap in the base, so the HB-side differences move £0. Those differences are the earnings, LCWRA and carer-element exceptions lost, reg 5, reg 75D(2), and the couple rate for reg 3(3) couples.
• LHA categories are unchanged. The EFRS has no AFIP and no reg 3(3) single claim (Model a Universal Credit claim by a member of a couple as a single person (UC Regs 2013 reg 3(3)) #2084's run found none).
• Diagnostics:
  • No family has both UC and HB before the cap.
  • No family had a positive benefit_cap_reduction without an award, so uk-data's cap targets are unchanged.
  • LHA_cap and uc_LHA_cap are unchanged everywhere.

Scripts and outputs: impact/ in the handover folder (dataset_impact.py, compare.py, r1/ and r2/branch_vs_base.json).

Tests

• New YAML, hand-computed from the law:
  • gov/dwp/benefit_cap_by_scheme.yaml (17 cases). Each scheme's exceptions:
    • UC reg 83(1)(a) LCWRA and (j) carer element, which are not HB exceptions; carer's allowance, which lifts both;
    • UC reg 82 earnings, which is not HB; HB reg 75E WTC, which is not UC;
    • HB reg 5 for a pension-age claimant, a mixed-age couple on UC (capped under both), a mixed-age couple off UC (HB pension-age regulations, no cap), and a partner on income-based JSA (HB Regs 2006 apply).
    • Reductions: UC reg 81 (excess 7,980 less childcare 3,000 = 4,980; childcare above the excess gives 0; no award gives 0); HB reg 75D(1) (HB 10,000 − 7,980 = 2,020); 75D(2) (5,000 → 26); HB below 50p a week (unreduced).
    • A reg 3(3) couple in London: UC 16,967, HB 25,323.
    • AFIP lifts both caps (UC reg 83(1)(c) with reg 2; HB reg 75F(1)(ea)).
  • housing_benefit/housing_benefit_lha_category.yaml (9 cases):
    • AFIP: excepted under UC Sch 4 para 29(5)(b) with reg 2, and under HB Sch 3 para 14;
    • HB young individual at 30 and at 35;
    • Sch 3 para 14(2)(b): a couple qualifies only if both members do;
    • an adult non-dependant defeats the premium, unless the non-dependant receives a qualifying benefit (para 14(4));
    • another family's claimant in the household;
    • an HB-only young person blocks both shared rates. With the two bedrooms both schemes give (UC Sch 4 para 10(1); HB reg 13D(3)(b)), that is category C.
• Rewritten for both schemes:
  • gov/dwp/benefit_cap.yaml (17). The reg 3(3) couple gets UC 14,753 and HB 22,020. The HB-only 19-year-old gives UC 14,753 and HB 22,020.
  • LHA_claimant_composition.yaml (19). The reg 3(3) couple gets UC A and HB B.
  • universal_credit/claims_as_single_person.yaml (27). The other member's PIP lifts the HB cap (75F) but not the UC cap (83). Earnings lift the UC cap but not the HB cap. A legacy-claiming reg 3(3) family is single for UC and a couple for HB.
• New property tests (test_benefit_cap_lha_scheme_split_properties.py, Hypothesis, derandomised, plus explicit examples of every scheme difference): differential tests against the parent commit's shared formulas. These are re-added under reference_ names through a structural Reform, so one simulation computes old and new for the same families. They are verbatim except for the names they read, the inlined stopgap helpers and the earnings exception's dead code. The reference awards read the current uc_deductions, which these single-household simulations leave at nil. Invariants below.
• Updated:
  • test_uc_single_claim_properties.py (Model a Universal Credit claim by a member of a couple as a single person (UC Regs 2013 reg 3(3)) #2084): HB's cap rate, exceptions, young-individual test and category equal the joint claimants' whatever the reg 3(3) flag says.
  • The HB LHA tests now pin housing_benefit_LHA_rate.
  • test_lha_uc_maximum.py, test_uc_deductions.py and test_abolish_benefit_cap_scenario.py (the scenario lifts both caps).
• Runs (targeted, one process at a time):
  • policyengine-core test policyengine_uk/tests/policy: 1,782 passed at c8fd1c9.
  • Split properties: 7 passed at c8fd1c9.
  • pytest on Model a Universal Credit claim by a member of a couple as a single person (UC Regs 2013 reg 3(3)) #2084's properties, HB LHA order, HB pension age, abolish-cap scenario, LHA maximum/freeze/UC maximum and UC deductions: 64 passed at c8fd1c9.
• Mutation checks: 10 of 10 killed (probes/mutate.py, run at c7bd4c0 against a detached copy). Each mutation was caught by the YAML files above, the split property file, or both:
  • M1: HB rate follows the reg 3(3) single claim (YAML and properties);
  • M2: UC reduction ignores the childcare costs element (YAML and properties);
  • M3: HB exception includes LCWRA (YAML and properties);
  • M4: LHA_cap reads the UC category's rate (properties);
  • M5: HB reduction ignores the 50p minimum (YAML and properties);
  • M6: the UC shared-rate test ignores reg 3(3) (YAML and properties);
  • M7: UC exception includes WTC (YAML);
  • M8: HB cap reaches pension-age claims (YAML);
  • M9: HB shared-rate test ignores the severe disability premium (YAML and properties);
  • M10: UC cap rate reads responsibility under either scheme (YAML and properties).

Invariants

For every generated family and every example:

1. Cap rate.
   • Where the UC and HB single-claimant rates agree, the old shared rate equals them.
   • Where they differ only through a reg 3(3) single claim, the old rate was the claimed scheme's (the Model a Universal Credit claim by a member of a couple as a single person (UC Regs 2013 reg 3(3)) #2084 stopgap: legacy → HB, otherwise UC).
   • Where they differ through responsibility, the old rate was the family rate if either scheme gave it.
   • HB never gives a couple the single-claimant rate.
2. Exceptions.
   • With nobody at State Pension age, no AFIP and no reg 3(3) single claim, the old exception is exactly the union of the two schemes' (UC ∪ HB). Wherever they agree, it is their value.
   • For a non-legacy reg 3(3) single claim, the old exception is UC's or HB's WTC exception.
   • The age and AFIP changes are intended (UC has no age exception; HB reg 5; AFIP now lifts both caps) and are pinned in YAML and the examples.
3. LHA.
   • Without AFIP, the old category is the new category of the scheme the family claims under.
   • With no reg 3(3) single claim, the UC and HB categories are equal.
4. Reductions.
   • uc_benefit_cap_reduction = max(excess − childcare costs element, 0) on an award, else 0.
   • 0 ≤ the HB reduction ≤ HB's excess.
   • HB after the cap ≥ min(HB before the cap, 50p × 52), and ≤ HB before the cap.
   • benefit_cap_reduction = UC + HB reductions.
   • No family has both UC and HB before the cap.
5. Awards. Where a scheme's cap equals the old cap, and neither reg 81's offset nor reg 75D(2)'s minimum applies, universal_credit / housing_benefit equal the award under the old shared cap.
6. LHA rate. LHA_cap = min(rent, housing_benefit_LHA_rate). That rate equals the UC category's BRMA_LHA_rate wherever the categories agree, so it is a differential between the two lookup paths.

test_examples_reach_the_cases checks that each example changes the result it is there for: reg 3(3) under UC and legacy, reg 81, the HB-only young person, AFIP, the mixed-age couple on UC, an HB family with LCWRA, and reg 75D(2).

Reviews

Independent Opus reviews through Subfleet. Round 1 (head 12ac785): REQUEST_CHANGES, one P2 and five P3s, all addressed in c8fd1c9. Round 2 (head c8fd1c9): APPROVE. Its two P3 notes:

• the PR body's evidence lines, synchronised here;
• AFIP inherits the pre-existing "any member" UC person scope, which Lift the benefit cap only for the support component and the people HB reg 75F and UC reg 83 name, and cap only the family's benefits #2076 narrows to the claimant (the composition branch uc-hb-split-on-2076 already does).

Coordination

Comments posted on each related PR, with the port each needs:

• Lift the benefit cap only for the support component and the people HB reg 75F and UC reg 83 name, and cap only the family's benefits #2076: per-scheme person scopes. A pre-resolved composition, uc-hb-split-on-2076, follows.
• Apply each scheme's own non-dependant test to the LHA shared accommodation rate #2030 and Give sharers, boarders and lodgers their own rent, tenure and LHA category #2006: names converged; their HB LHA versions supersede these.
• Apply the benefit cap to mixed-age couples on Universal Credit, and keep them off pensioner Council Tax Reduction #1944: this PR includes its cap half.
• Use each rule's own Universal Credit earned income in the benefit cap, targeted childcare and local CTR #1999 and Fix benefit cap exemption defects (#1818) #1820: the earnings exception moves to the UC file.
• Give the UC LCWRA and carer elements, the work allowance and the benefit cap exceptions on the claimants' circumstances only #1989: UC claimant-only exceptions go in the UC file.
• Reconcile UC deduction and benefit cap components under the protected floor #1819: uc_benefit_cap_reduction name.
• Model a Universal Credit claim by a member of a couple as a single person (UC Regs 2013 reg 3(3)) #2084: the base.

The landing job (launchd) waits for #2084 to merge, then retargets, merges main, tests, reviews the head and merges on gates.

axiom:

• encoded-correct at rulespec-uk 840c51f:
  • uk/regulation/uksi/2013/376/80A (80A.test.yaml: single_not_greater_london_no_child_normal_home, single_not_greater_london_responsible_for_child_no_home);
  • .../81 (childcare costs element greater than excess so no reduction applies);
  • .../schedule/4/paragraph/27 and /28 (renter_meets_all_specified_renter_conditions, renter_not_single_or_claiming_as_single).
• queued:
  • UC reg 82: Round the UC reg 82 earnings threshold to whole pounds (reg 6(1A)(za)), date it from 2017, and date the national living wage (PE parity: policyengine-uk#1999) TheAxiomFoundation/rulespec-uk#399.
  • UC regs 79/83 and HB reg 5: Survey structure, metadata and testing for personal benefits #389, Add semver actions #425.
  • UC Sch 4 para 29 and reg 2 "attendance allowance": Survey structure, metadata and testing for Housing Benefit #384, Test that the HITC doesn't exceed Child Benefit #411.
  • HB regs 2, 13D and 75CA: Add if eligible to would_claim variable descriptions #357. HB Sch 3 para 14: Survey structure, metadata and testing for other legacy benefits #386. HB regs 75A, 75C, 75D, 75E and 75F: Add semver actions #425.
  • Addenda for this PR's cases are posted on Add if eligible to would_claim variable descriptions #357 (reg 3(3) couple: single for UC, couple for HB), Add semver actions #425 (HB family with only a UC element; reg 75D(2) 50p minimum; reg 81 pipeline regressions), Survey structure, metadata and testing for Housing Benefit #384/Add if eligible to would_claim variable descriptions #357 (AFIP) and Survey structure, metadata and testing for personal benefits #389 (pension-age HB amounts).

🤖 Generated with Claude Code

[MaxGhenis]

Coordination from #2084, which this PR is stacked on. #2084's head moved to fa1e7448b after its round-2 review, and the shared-rules helpers this PR removes changed:

• policyengine_uk/utils/uc_work_related_requirements.py gains stays_on_legacy_benefits(benunit, period), which is claims_legacy_benefits & ~would_claim_uc. That is the continuing-award route housing_benefit_eligible uses.
• single_claim_in_rules_shared_with_legacy_benefits and other_member_of_single_claim_in_shared_rules now gate on it instead of on claims_legacy_benefits alone. Round 2 reproduced the bug this fixes: a family that reports Housing Benefit but is calculated on UC lost the UC rules in LHA_category, uc_housing_costs_element and the cap.
• claims_as_single_person.yaml now has two cases where it had one legacy case:
  • "reports HB but claims UC": single cap of 14,753, no exception for the partner's PIP, shared rate (A);
  • "stays on legacy benefits" (would_claim_uc: false): couple rate, the partner's PIP lifts the cap under HB reg 75F(1)(ea), LHA B.
• test_uc_single_claim_properties.py restructured its example families (EXAMPLE_INDEX, nine families, LCWRA and caring kept apart for reg 29(4)).

When #2084 is merged into this branch, keep this PR's deletion of the helpers. Then check that the per-scheme variables pass those two YAML cases, since they pin the UC-vs-HB routing the split has to keep. #2084's round-3 review (subfleet 20261003-101137-reg33-review-r3) is reviewing fa1e7448b.

[MaxGhenis]

Overlap with #1978 (Count only claimants' income in Universal Credit), for whichever of the two merges second.

#1978 limits two of the things this PR moves to the claimant and partner (is_uc_assessed_claimant):

• The earnings exception. UC Regs reg 82(1)(a) tests "the claimant's earned income or, if the claimant is a member of a couple, the couple's combined earned income". Count only claimants' income in Universal Credit #1978 sums is_benefit_cap_exempt_earnings over is_uc_assessed_claimant. This PR moves that formula into is_uc_benefit_cap_exempt_earnings, which still sums every member.
• The capped total. WRA 2012 s.96(1) and reg 80(1) count "the welfare benefits to which a single person or couple is entitled". Count only claimants' income in Universal Credit #1978 sums the person-level benefits in benefit_cap_reduction over is_uc_assessed_claimant. This PR moves the list into benefit_cap_welfare_benefits (add(benunit, period, CAPPED_BENEFITS)), which still sums every member.

The intended end state is this PR's split, with both new variables summing person-level amounts over is_uc_assessed_claimant (add_for_members(benunit, period, CAPPED_BENEFITS, claimants) for the total). #1978's YAML cases in universal_credit/dependants_income.yaml pin both. A qualifying young person's £12,000 must not meet the exception, and their contributory JSA must not be in the total. Rename the variables those cases read when the split lands.

#1978's head is 0e74b27d6, merged with main.