Reduce Carer's Allowance and Carer Support Payment by overlapping benefits

[MaxGhenis]

Fixes #1953

Problem and implementation

Carer's Allowance (CA) and Carer Support Payment (CSP) previously paid their unreduced modeled amounts even when another benefit overlapped. This PR separates the pre-overlap amounts from payable amounts and computes max(0, pre_overlap - overlapping_benefits).

• carers_allowance_pre_overlap and carer_support_payment_pre_overlap retain the previous formulas.
• Each overlap total sums overlapping_state_pension, incapacity benefit, SDA, maternity allowance, contribution-based JSA and contributory ESA through a programme parameter list.
• New State Pension overlaps in full, including protected payment. For old State Pension, the helper excludes the modeled additional-pension share and preserves that share under State Pension reforms.
• A directly supplied State Pension total with no components overlaps in full as an input convention. Reported old pension is split at the full basic-rate cap; that estimate cannot identify basic-pension increments above the cap or additional pension inside a partial pension.
• is_entitled_to_carer_benefit records positive pre-overlap entitlement or a carer benefit in payment. Positive payable CSP continues to determine Scottish Carer Supplement through its existing formula.

The reduction follows OBR regulation 4, regulation 12 and CSP regulation 16(2), (3) and (6). Old additional pension and graduated retirement benefit are excluded; the reported-total split is a model assumption, not a statutory component classification.

Review fixes (607a815c)

An independent review of the earlier head found nine problems; 607a815c fixes them:

• Pension Credit carer additions and carer premiums count is_entitled_to_carer_benefit for is_claimant_or_partner; caring hours alone no longer establish entitlement for these rules (SPC Sch I para 4, HB Sch 3 para 17, HB (SPC) Sch 3 para 9). CA entitlement normally requires a claim or treatment as claiming under SSAA s.1.
• The UC non-dependant housing deduction exemption reads receives_carer_benefit, matching the receipt conditions in UC Sch 4 para 16(2)(g), (ga). The hours route stays available to the UC carer element; UC reg 30(2) does not require a CA claim.
• Property tests distinguish payable benefits from underlying entitlement, fix the State Pension draws inherited from Count Carer's Allowance and Carer Support Payment as Pension Credit income #1952, and assert the Pension Credit gain from claiming an allowance reduced to nil. The reference identifies pension type from drawn age and sex and labels the reported-total split as a model assumption.
• YAML cases use legally appropriate disability-benefit inputs and distinguish claimant/partner status from receipt; substitutions in unused cap benefit lists are reverted. Two older carer premium cases (care.yaml) now set entitlement on each person instead of num_carers, which the premium no longer reads.

Annual amounts

The model is annual, so the reduction compares annual amounts: max(0, pre_overlap - overlapping_benefits). The law works by period: OBR reg 4(1)(a) addresses overlapping periods, reg 14 part weeks, and CSP reg 16(2) each award week. With year-round carer entitlement, the annual comparison equals the weekly rule when the other benefit is paid at a constant rate all year. Where the other benefit is above the carer rate in some weeks and lower or absent in others, the annual comparison pays less than the weekly rule would. Annual inputs carry no dates, so the model cannot do better; the variables' documentation says so.

Impact on the Enhanced FRS

Real Microsimulation runs on the Enhanced FRS 2024-25 (policyengine-uk-data 1.57.4, SHA-256 03fe15e4…68d4), comparing main aa67bdb4 with this branch at f35f25b2 (later commits change tests only), 2025 to 2028:

• Carer's Allowance falls, and household net income falls with it, for fewer than 10 sample households in each year; no household gains. Because so few records move, no amounts are given.
• Carer Support Payment, Scottish Carer Supplement, Pension Credit, Housing Benefit, Council Tax Reduction and Universal Credit do not change.

An earlier run against #1952's head found that the Carer's Allowance reduction comes from contributory ESA at working age, with no reduction from State Pension.

Coordination

• Count Carer Support Payment as Council Tax Reduction income #1992 (Scottish CTR counts CSP). On main, CTR income does not count CSP; Count Carer Support Payment as Council Tax Reduction income #1992 adds it. Until Max rules on d861 (how Scottish CTR counts CSP once reg 16(2) cuts it), CTR should read carer_support_payment_pre_overlap, which leaves CTR as it is today. Whichever of Count Carer Support Payment as Council Tax Reduction income #1992 and this PR lands second wires that in; Count Carer Support Payment as Council Tax Reduction income #1992 carries two tripwire cases that fail if CTR income drops the CSP.
• Pay the legacy carer premium per qualifying claimant or partner; IS carer route through them only #2001 (carer premium per qualifying person). Main's couple carer premium parameter holds the single rate; Pay the legacy carer premium per qualifying claimant or partner; IS carer route through them only #2001 pays the premium per qualifying claimant or partner. Both PRs edit carer_premium.py, so whichever lands second resolves the overlap.

Remaining scope and evidence

UC regulation 66(1)(b)(iiia) limits CSP income to the amount the claimant would receive with CA entitlement. With this model's matching rates and overlap lists, hypothetical overlap-adjusted CA equals reduced CSP, narrowing the earlier UC pre/post-overlap question. The separate Scottish pension-age CTR treatment remains unresolved: regulation 27(3), (5) specifies overlap adjustments under the 1979 Regulations but does not name CSP regulation 16(2). No new CTR treatment is implemented here; see Coordination.

Other statutory overlapping benefits without modeled inputs, dependency increases and deferred/notional State Pension remain outside this PR. The annual model also cannot reproduce all within-year changes in supplement receipt; CSP regulation 14A specifies each award week in which CSP is payable.

Primary legislation was read from legislation.gov.uk XML during review.

🤖 Generated with Claude Code

[MaxGhenis]

Coordination with #2076, stacked on #2027.

#2076 removes the unused benefit sums from is_benefit_cap_exempt_other.py and is_benefit_cap_exempt_earnings.py. It also moves the afcs and ESA terms out of is_benefit_cap_exempt_other into is_benefit_cap_exempt_health_disability, limited to the claimant and partner. Before, any member's AFCS or contributory ESA lifted the cap.

Whichever lands second: keep this PR's age or earnings test, and drop the afcs and esa_support_component terms and the dead QUAL_* lists from _other and _earnings.

[MaxGhenis]

A wording fix for is_carer_for_benefits' documentation, since this PR rewrites it. The independent review of #2088 (UC childcare work condition, reg 32) flagged it.

The documentation says the hours limb "does not check that the person cared for receives a qualifying disability benefit (the second limb of regulation 30)". Current UC Regs 2013 reg 30 has two heads:

• (1)(a) satisfying the conditions for carer's allowance (or would, but for the earnings limit or Scottish residence);
• (1)(b) entitlement to carer support payment.

The qualifying-benefit requirement isn't a limb of reg 30. It's one of the Carer's Allowance conditions that (1)(a) imports. SSCBA 1992 s.70(1) requires caring for a "severely disabled person", and s.70(2) defines one as a person "in respect of whom there is payable either an attendance allowance or a disability living allowance by virtue of entitlement to the care component at the highest or middle rate or personal independence payment by virtue of entitlement to the daily living component ...".

The hours branch also doesn't apply reg 30(3): "a person does not have regular and substantial caring responsibilities for a severely disabled person if the person derives earned income from those caring responsibilities."

Suggested wording:

The hours limb tests hours alone, as carers_allowance does. It does not check that the person cared for is a severely disabled person (one receiving a qualifying disability benefit, SSCBA 1992 s. 70(2), a Carer's Allowance condition that regulation 30(1)(a) imports), nor exclude a carer paid for the caring (regulation 30(3)). So a survey hours field counts caring for anyone, and a dataset's take-up input carries that simplification.

A smaller point: "the underlying entitlement" overstates what the hours branch establishes. "An approximation of the underlying entitlement" would be accurate.

🤖 Generated with Claude Code

[MaxGhenis]

Merged under Max's PE-UK merge-on-gates rule (decision d783: merge on gates; the rule: CI green on the merged head, an independent review approving that exact head, impact stated from a real microsimulation run, stack order respected).

• Independent review: subfleet 20261003-101021-mt-review-1994-r2 (GPT-6.1 Sol) approved d5abad83 with no blocking finding: all nine findings of the earlier review are resolved, and annual netting is a disclosed data limitation (the law works by week; annual inputs carry no dates).
• Delta review: subfleet 20261003-093751-mt-review-1994-mm approved e2a4d672, which is d5abad83 plus a clean merge of main 2c942867 (Cut PR CI from hours to about 20 minutes: Linux arm64, 4 xdist workers, cancel superseded runs #2115, Date the mixed-age couple Pension Credit exclusion and model the SI 2019/37 saving #1940, Read is_claimant_or_partner for Pension Credit capital; make the Lifetime ISA dependant test exercise the flag #2073): the tree equals the automatic merge, and none of main's changes touches this PR's files or variables.
• CI: all checks pass on e2a4d672 (Linux Test job).
• Impact: real runs on the Enhanced FRS 2024-25 (1.57.4), main aa67bdb4 against f35f25b2 (later commits change tests only), as stated in the description.
• Coordination: Count Carer Support Payment as Council Tax Reduction income #1992 adds Carer Support Payment to Scottish CTR income; when it lands it reads carer_support_payment_pre_overlap until Max rules on d861.