[MaxGhenis]

Addresses #2874
axiom: n/a: microsimulation-only: stored inputs for engine draws, no rule changes

This PR contains #2873's two commits (the engine-randomness guard) and lands after #2873.

What and why

Three new yearly inputs, with no formula:

• uc_new_claimant_health_element_draw (benefit unit, float, default 1.0): a uniform in [0, 1) that the dataset build stores. In each Universal Credit rebalancing year with no status for the year, add_universal_credit_reform gives a benefit unit the new-claimant LCWRA rate when the draw falls below new_claimant_share.
• pip_phase_in_draw (person, float, default 1.0): the PIP phase-in scenario removes a person's PIP in a year from 2025 to 2029 when the draw falls below that year's share.
• would_claim_student_loan (person, bool, default False): the stored take-up decision that uprate_student_loan_plans uses for new borrowers.

Each consumer uses the stored input when the dataset supplies it and runs its own seeded draw, unchanged and inline, when it does not. The UC modifier and the PIP scenario ask input_source whether a supplied draw reaches the year, read it through Simulation.calculate, and compare it with the share in float64. Student loan uprating reads the column from the projected table after checking its raw values. No published dataset carries these columns yet, so outputs on today's data change only where the tightened helper below changes an answer.

Reading a stored draw

utils/stored_draws.py registers the two draws with their entity, value type and definition period. input_source(population, name, period) returns the period, branch, tier and sequence number of the supplied input policyengine-core reads, None where no supplied input reaches the period, and raises otherwise. It changes nothing in storage and returns no array. It refuses:

• a request other than one whole year in storage form (a month, year:2026:2, month:2026-06:12, year:2025-01-15);
• a current or holder definition that changes the entity, type or period, or adds a formula, uprating, defined_for, calculate_output, adds, subtracts or requires_computation_after; a neutralised or abolished draw; core's macro cache; carry turned off where the read needs it;
• a holder with a disk tier, naming Storage keys need a structured (branch, period) scheme: str(period) is lossy and separators collide with branch names policyengine-core#526;
• a non-derived value in the slot core reads that no one supplied; a derived value whose carry source no one supplied, or that differs from its source; and, with no supplied source, a derived value other than the holder's default.

In a simulation built from data, Simulation.calculate runs the check after its input-lifecycle and stale-record cleanups, drops the request's fast-cache entry, and for a source-backed draw calls core with map_to=None, checks that core's answer equals the source's array (same dtype and shape) and that the source has not changed, then maps it. calculate_add, calculate_divide and calculate_output refuse a registered draw. A context variable counts running pe-uk calculations on any simulation, and set_input refuses a new draw while one runs or while the holder stores a derived value of the draw. Situations keep core's path.

Supplied-input helpers

SUPPLIED_INPUT_VARIABLES now holds the three new columns. set_model_value refuses them. A recorded key now counts only when its branch is the one core reads for the period and the tier core reads there (memory before disk) still holds the input. latest_supplied_input_period ranks with core's _latest_input_key.

What this changes for existing callers (supplied_input, supplied_input_periods, supplied_by, latest_supplied_input_period, used by current_education, the maintenance loan, PIP, trading allowance, Class 4 loss and housing benefit formulas):

• a value cached as non-derived over an input in the same slot no longer counts as supplied (test_a_value_cached_over_an_input_in_its_slot_is_not_supplied);
• on a child branch, a parent's input under a value the child stores no longer counts (test_a_child_branch_value_over_a_parent_input_is_not_supplied_on_the_child);
• an input on disk under a value cached in memory no longer counts (test_an_input_on_disk_counts_only_when_memory_does_not_hide_it);
• of supplied periods before the request, the latest is now the one core's carry-over would pick: a period of the variable's own unit before another unit, and of two that start on one day the one that ends last (test_two_periods_starting_on_one_day_rank_by_core_order).

Calculation itself never caches a value over a supplied input, so these cases arise only from low-level holder writes or branch caches; the required test files below pass unchanged.

The core Dataset route

Before it exports, Simulation.build_from_dataset refuses a dataset that carries any stored column (the UC deduction draws, months_since_last_birthday, warm_home_discount_random_draw and the three new columns) when any person, benefit unit or household identifier fails to survive the int32 cast, naming the entity and identifiers. It also refuses a dataset whose stored columns, attends_private_school_random_draw, uc_receives_new_claimant_health_element or attends_private_school it supplies for some period but not the first, or whose draws change between periods.

Datasets the route now refuses: core-format datasets carrying one of those columns with identifiers beyond int32, and core-format datasets supplying one of them only for later periods, or with a draw that changes between periods. None of pe-uk's own core-route fixtures carries such a column, so the route refuses none of them.

Core versions

QUALIFIED_CORE_VERSIONS records 3.33.3 and 3.34.1. tests/code_health/test_core_version_gate.py fails when uv.lock or the installed core holds another version, and says what to rerun before adding one. It reads uv.lock from the source tree or the directory the tests run from, so it runs without a skip when CI tests the built wheel.

Invariants

• Qualified core: the lock and the installed core are 3.33.3 or 3.34.1.
• Output-neutral by construction: without the columns each consumer runs today's draw; with columns built by the reference encoder from today's draws, the UC statuses, LCWRA amounts and PIP amounts agree bit for bit on the DataFrame and core Dataset routes.
• Representation: an encoded draw lies in [0, 1), survives a float32 round trip, sits within 2^-24 of its legacy draw, and each consumer compares it in float64, so it keeps the legacy decision at every covered threshold (property test). Compared in float32, a stored 3/8 would fall on the wrong side of a share of 3/8 + 2^-28.
• Reformability: new-claimant status is monotone in the share and PIP phase-out in the phase-in share (property tests); no student loan call passes a rate, and the stored decision holds in every projected year.
• Fail closed (read rules): every read of a registered draw passes input_source before core and the answer check after; ADD, DIVIDE and output refuse draws; the fast cache never answers one.
• Cache survival: a surviving draw cache unequal to its current proven source raises; an invalidated cache recomputes from the current source.
• Precedence unchanged: a status supplied for the year wins; one supplied only earlier leaves the later year to the draw; a repeated modifier, a reform after construction and an export replayed under another share keep the statuses.
• Keys and order: the core route refuses stored columns with identifiers that do not survive the int32 cast, and stored columns not supplied for the first period.
• Determinism: applying the PIP scenario with stored draws for every year leaves numpy's global state as it was.

Test plan

• test_supplied_input_tightening.py: registration, ranking (with a Hypothesis property against core's order), the tightened key and the set_model_value refusal.
• test_stored_draw_input_source.py: provenance, requests, definitions, disk tier, dispatch, setter, lifecycle, restore and the differential against core's own calculate.
• test_stored_draw_consumers.py: each consumer with and without its column, precision, precedence, validation and properties.
• test_stored_draw_core_route.py: identities for each entity, supplied periods, and the with/without differential on both routes.
• code_health/test_core_version_gate.py and code_health/test_stored_draw_reads.py (no package read of a draw skips calculate).

On core 3.34.1 (the lock) and 3.33.3 (uv run --frozen --with 'policyengine-core==3.33.3', which printed 3.33.3), the 17 required existing files, these six files and the five other core-Dataset-route files gave 1069 passed, 0 failed on each. policyengine_uk/tests/code_health gave 3556 passed. Mutations of each refusal, of each consumer's float64 promotion, of the fast-cache eviction, of the set_model_value refusal, of both core-route checks, of #6's validation and of its loader each fail a test. ruff format --check, ruff check and git diff --check pass.

What later stages finish

Stage 2 adds protected storage and sealed populations, with a storage check inside input_source. Phase 2 fails closed: it removes the seeded fallbacks, registers the other required draws and outcomes, and adds months_since_last_birthday's answer check and inclusive lookup.

---

Generated by Claude Code

[github-actions]

Aggregate impact on certified data: pass

Base d4655eb56c against head 0728128dc8, both on enhanced_frs_2024_25.h5 (policyengine-uk-data 1.58.1, sha256 056e80fd8e91), fiscal years 2025-26 to 2031-32. Each year is a full microsimulation run on each side.

Checks: 0 broken by this change, 1 failing on both sides, 0 fixed. Moves flagged for review: 0 (thresholds in report_spec.yaml; a flag does not fail the job).

Workflow run and full report

Notes

• In the years a figure from fewer than 10 records is suppressed (spending.disabled_students_allowance), every total containing it, and the decile incomes, are rebuilt from their other components, so no published total includes it. Those totals are marked †. A change is withheld where the two sides leave out different figures and can't be lined up.

Moves flagged for review

None.

Spending by benefit and service

Measure	2025-26	2026-27	2027-28	2028-29	2029-30	2030-31	2031-32
Disabled Students' Allowance	suppressed	suppressed	suppressed	suppressed	suppressed	suppressed	suppressed

Caseloads

Measure	2025-26	2026-27	2027-28	2028-29	2029-30	2030-31	2031-32
Disabled Students' Allowance	suppressed	suppressed	suppressed	suppressed	suppressed	suppressed	suppressed

Household net income by decile

No household's net income changes in any year.

No change in any year: receipts by tax head; government balance, each component counted once; model totals; household income totals; population; poverty rates; people in poverty; inequality; mean household net income in each side's own deciles; standard reform costings (change in gov_balance); standard reforms: change in each reform's target.

Checks failing on both base and head (1)

• VAT excluding private school fees is never negative (sign:vat): 2025-26: 76 units below zero, a weighted £-53,888,684 in total; 2026-27: 76 units below zero, a weighted £-55,777,260 in total; 2027-28: 76 units below zero, a weighted £-57,727,917 in total

Counted-once check

Each of 92 components was raised by £1 per unit in 2026-27, and every head of its totals was read household by household: its own head must rise by exactly £1, no other tax head may move, no other benefit may rise, and the model's own total must move by what its heads moved. A head that breaks a rule is measured again twice: with every other head held at its baseline value, and with every other head held at its value after the first £1 while the component rises again. It fails where either still shows the response. 0 failed; 0 were skipped.

• widowed_parents_allowance: pension_credit responds only through other heads in fewer than 10 households (other heads that moved there: carers_allowance; gov_spending; not a failure)
• widowed_parents_allowance: pension_credit responds only through other heads in fewer than 10 households (other heads that moved there: carers_allowance; household_benefits; not a failure)

Provenance

Side	Commit	Runtime	Environment hash	Partition hash	Time
base	main d4655eb56c	uk 2.175.3 (files 889511591b1d), core 3.34.1, py 3.13.18 aarch64	2be386090644	3bcfb3473960	2559.39s
head	#2877 merged into main 0728128dc8	uk 2.175.3 (files f2a1599c1f3b), core 3.34.1, py 3.13.18 aarch64	2be386090644	3bcfb3473960	2587.65s

Dataset: hf://policyengine/policyengine-uk-data-private/enhanced_frs_2024_25.h5@2526edbbb687a3b54dbb11272e5389e4b62d2ac2, sha256 056e80fd8e9151d78f432a25cde863340baee81304c6216a37fb575ce8563784 (verified on both sides), policyengine-uk-data 1.58.1.

Receipts by tax head: head levels

Measure (head)	2025-26	2026-27	2027-28	2028-29	2029-30	2030-31	2031-32
Final charge on cash interest in non-cash ISAs	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Lifetime ISA withdrawal charge	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Income tax	£294.46bn	£315.23bn	£335.82bn	£351.28bn	£366.96bn	£385.36bn	£399.99bn
National Insurance (employee and self-employed)	£51.70bn	£54.14bn	£56.13bn	£57.73bn	£59.76bn	£61.64bn	£63.51bn
National Insurance (employer)	£148.71bn	£155.37bn	£160.88bn	£165.09bn	£172.06bn	£177.36bn	£182.57bn
Employer NI change borne by capital	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Employer NI change borne by consumers	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Capital gains tax	£12.60bn	£13.15bn	£13.60bn	£14.11bn	£14.67bn	£15.24bn	£15.80bn
Student loan repayments	£7.82bn	£8.13bn	£8.39bn	£8.58bn	£8.79bn	£9.04bn	£9.29bn
VAT excluding private school fees	£249.37bn	£256.87bn	£266.33bn	£272.70bn	£278.97bn	£285.24bn	£291.59bn
Change in VAT from its baseline	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
VAT on private school fees	£1.95bn	£2.01bn	£2.09bn	£2.14bn	£2.20bn	£2.26bn	£2.31bn
Change in private school VAT from its baseline	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Fuel duties	£24.71bn	£24.13bn	£26.00bn	£26.83bn	£26.51bn	£25.78bn	£24.63bn
Alcohol duties	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Tobacco duties	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Vehicle excise duties	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Betting and gaming duties	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
TV licence fee	£4.26bn	£4.40bn	£4.41bn	£4.42bn	£4.43bn	£4.44bn	£4.45bn
Council tax	£49.21bn	£52.16bn	£54.89bn	£57.95bn	£61.16bn	£64.47bn	£67.91bn
High value council tax surcharge	£0.00bn	£0.00bn	£0.00bn	£0.48bn	£0.49bn	£0.50bn	£0.51bn
Northern Ireland domestic rates	£0.55bn	£0.58bn	£0.60bn	£0.63bn	£0.66bn	£0.69bn	£0.72bn
Business rates	£34.68bn	£36.20bn	£38.00bn	£39.46bn	£42.27bn	£43.25bn	£44.29bn
Stamp duty land tax on the household's own purchases	£6.88bn	£7.32bn	£7.66bn	£8.06bn	£8.47bn	£8.91bn	£9.35bn
Stamp duty land tax paid by companies	£4.72bn	£4.57bn	£5.29bn	£6.03bn	£6.37bn	£6.92bn	£7.45bn
Land transaction tax (Wales)	£0.07bn	£0.08bn	£0.08bn	£0.09bn	£0.10bn	£0.10bn	£0.11bn
Land and buildings transaction tax (Scotland)	£0.31bn	£0.32bn	£0.33bn	£0.35bn	£0.36bn	£0.38bn	£0.40bn
Unspecified tax change borne by capital	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Unspecified tax change borne by consumers	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Wealth tax	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Wealth tax excluding the main residence	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Land value tax	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Carbon tax	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn

Spending by benefit and service: head levels

Measure (head)	2025-26	2026-27	2027-28	2028-29	2029-30	2030-31	2031-32
Lifetime ISA bonus	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
State Pension	£121.68bn	£125.92bn	£126.72bn	£129.48bn	£132.98bn	£136.65bn	£140.41bn
Pension Credit	£6.21bn	£6.46bn	£6.68bn	£6.82bn	£6.89bn	£7.07bn	£7.22bn
Winter Fuel Payment	£1.86bn	£1.85bn	£1.79bn	£1.77bn	£1.78bn	£1.78bn	£1.78bn
Pension Age Winter Heating Payment (Scotland)	£0.19bn	£0.20bn	£0.20bn	£0.21bn	£0.21bn	£0.22bn	£0.22bn
Universal Credit	£75.48bn	£81.56bn	£84.02bn	£86.07bn	£87.22bn	£88.76bn	£89.38bn
Housing Benefit	£8.56bn	£8.51bn	£8.83bn	£9.05bn	£9.28bn	£9.56bn	£9.83bn
Council Tax Reduction	£2.07bn	£2.20bn	£2.32bn	£2.45bn	£2.59bn	£2.73bn	£2.87bn
Employment and Support Allowance (income-related)	£0.79bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Employment and Support Allowance (contribution-based)	£5.20bn	£5.37bn	£5.56bn	£5.69bn	£5.82bn	£5.95bn	£6.09bn
Jobseeker's Allowance (income-based)	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Jobseeker's Allowance (contribution-based)	£0.29bn	£0.30bn	£0.31bn	£0.31bn	£0.32bn	£0.33bn	£0.34bn
Income Support	£0.11bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Working Tax Credit	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Child Tax Credit	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Incapacity Benefit	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Personal Independence Payment	£26.95bn	£28.03bn	£29.05bn	£30.09bn	£30.75bn	£31.51bn	£32.21bn
Disability Living Allowance	£7.49bn	£7.79bn	£8.07bn	£8.36bn	£8.55bn	£8.76bn	£8.95bn
Attendance Allowance	£8.68bn	£9.03bn	£9.36bn	£9.69bn	£9.90bn	£10.15bn	£10.38bn
Carer's Allowance	£4.48bn	£4.66bn	£4.83bn	£5.00bn	£5.11bn	£5.27bn	£5.42bn
Carer Support Payment (Scotland)	£0.31bn	£0.32bn	£0.33bn	£0.34bn	£0.35bn	£0.36bn	£0.37bn
Carer's Allowance Supplement (Scotland)	£0.00bn	£0.04bn	£0.04bn	£0.05bn	£0.05bn	£0.05bn	£0.05bn
Severe Disablement Allowance	£0.03bn	£0.03bn	£0.03bn	£0.03bn	£0.03bn	£0.03bn	£0.03bn
Industrial Injuries Disablement Benefit	£0.50bn	£0.52bn	£0.54bn	£0.55bn	£0.56bn	£0.58bn	£0.59bn
Armed Forces Compensation Scheme	£0.61bn	£0.63bn	£0.65bn	£0.66bn	£0.68bn	£0.69bn	£0.71bn
War Widow's or Widower's Pension	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Child Benefit	£16.19bn	£16.82bn	£17.39bn	£18.00bn	£18.39bn	£18.84bn	£19.25bn
Scottish Child Payment	£0.49bn	£0.52bn	£0.53bn	£0.55bn	£0.56bn	£0.57bn	£0.56bn
Two Child Limit Payment (Scotland, counterfactual)	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Healthy Start vouchers	£0.05bn	£0.05bn	£0.05bn	£0.05bn	£0.05bn	£0.05bn	£0.05bn
Maternity Allowance	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Statutory Maternity Pay	£3.30bn	£3.41bn	£3.54bn	£3.62bn	£3.70bn	£3.78bn	£3.87bn
Statutory Paternity Pay	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Statutory Sick Pay	£1.12bn	£1.16bn	£1.20bn	£1.23bn	£1.26bn	£1.29bn	£1.32bn
Sure Start Maternity Grant	£0.01bn	£0.01bn	£0.01bn	£0.01bn	£0.01bn	£0.01bn	£0.01bn
Bereavement Support Payment	£0.67bn	£0.69bn	£0.71bn	£0.73bn	£0.75bn	£0.76bn	£0.78bn
Widowed Parent's Allowance	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Tax-Free Childcare	£0.56bn	£0.57bn	£0.57bn	£0.58bn	£0.60bn	£0.61bn	£0.59bn
Extended childcare entitlement	£2.99bn	£3.50bn	£3.59bn	£3.71bn	£3.78bn	£3.86bn	£3.93bn
Universal childcare entitlement	£2.06bn	£2.22bn	£2.29bn	£2.37bn	£2.43bn	£2.48bn	£2.53bn
Targeted childcare entitlement	£0.50bn	£0.51bn	£0.52bn	£0.54bn	£0.55bn	£0.57bn	£0.56bn
Childcare Offer for Wales	£0.26bn	£0.28bn	£0.28bn	£0.29bn	£0.30bn	£0.31bn	£0.32bn
Care to Learn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Childcare Grant	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Parents' Learning Allowance	£0.20bn	£0.20bn	£0.20bn	£0.20bn	£0.20bn	£0.20bn	£0.20bn
Adult Dependants' Grant	£0.06bn	£0.06bn	£0.04bn	£0.04bn	£0.04bn	£0.04bn	£0.04bn
Travel Grant	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Disabled Students' Allowance	suppressed	suppressed	suppressed	suppressed	suppressed	suppressed	suppressed
16 to 19 Bursary Fund	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
NHS spending	£203.89bn	£204.30bn	£204.56bn	£204.91bn	£205.34bn	£205.85bn	£206.35bn
State education spending	£0.02bn	£0.02bn	£0.02bn	£0.02bn	£0.02bn	£0.02bn	£0.02bn
Transport subsidy spending	£25.05bn	£25.10bn	£25.14bn	£25.18bn	£25.23bn	£25.30bn	£25.36bn
Cost-of-living support payment	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Energy Bills Rebate	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Household Energy Payment	£0.00bn	£2.11bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Energy Price Guarantee subsidy	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Basic income	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Disability basic income	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn
Other public spending budget change	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn

Caseloads: head levels

Measure (head)	2025-26	2026-27	2027-28	2028-29	2029-30	2030-31	2031-32
Lifetime ISA bonus	0k	0k	0k	0k	0k	0k	0k
State Pension	11,264k	11,145k	10,819k	10,700k	10,723k	10,750k	10,776k
Pension Credit	1,489k	1,484k	1,476k	1,454k	1,452k	1,457k	1,466k
Winter Fuel Payment	7,844k	7,783k	7,473k	7,375k	7,391k	7,409k	7,427k
Pension Age Winter Heating Payment (Scotland)	803k	802k	800k	797k	799k	801k	802k
Universal Credit	6,342k	6,418k	6,408k	6,369k	6,363k	6,343k	6,295k
Housing Benefit	1,249k	1,182k	1,181k	1,164k	1,164k	1,166k	1,168k
Council Tax Reduction	3,180k	3,199k	3,205k	3,218k	3,233k	3,244k	3,251k
Employment and Support Allowance (income-related)	71k	0k	0k	0k	0k	0k	0k
Employment and Support Allowance (contribution-based)	719k	720k	721k	722k	724k	726k	728k
Jobseeker's Allowance (income-based)	0k	0k	0k	0k	0k	0k	0k
Jobseeker's Allowance (contribution-based)	67k	67k	67k	67k	67k	68k	68k
Income Support	25k	0k	0k	0k	0k	0k	0k
Working Tax Credit	0k	0k	0k	0k	0k	0k	0k
Child Tax Credit	0k	0k	0k	0k	0k	0k	0k
Incapacity Benefit	0k	0k	0k	0k	0k	0k	0k
Personal Independence Payment	3,567k	3,575k	3,579k	3,585k	3,593k	3,602k	3,611k
Disability Living Allowance	1,291k	1,294k	1,296k	1,298k	1,300k	1,304k	1,307k
Attendance Allowance	1,695k	1,698k	1,700k	1,703k	1,707k	1,711k	1,715k
Carer's Allowance	1,034k	1,037k	1,038k	1,040k	1,042k	1,060k	1,062k
Carer Support Payment (Scotland)	71k	71k	71k	72k	72k	72k	72k
Carer's Allowance Supplement (Scotland)	0k	71k	71k	72k	72k	72k	72k
Severe Disablement Allowance	4k	4k	4k	4k	4k	4k	4k
Industrial Injuries Disablement Benefit	137k	137k	137k	138k	138k	138k	139k
Armed Forces Compensation Scheme	93k	93k	94k	94k	94k	94k	94k
War Widow's or Widower's Pension	0k	0k	0k	0k	0k	0k	0k
Child Benefit	8,123k	8,120k	8,120k	8,130k	8,145k	8,161k	8,178k
Scottish Child Payment	351k	352k	352k	353k	350k	348k	337k
Two Child Limit Payment (Scotland, counterfactual)	0k	0k	0k	0k	0k	0k	0k
Healthy Start vouchers	200k	200k	200k	201k	201k	201k	202k
Maternity Allowance	0k	0k	0k	0k	0k	0k	0k
Statutory Maternity Pay	333k	333k	334k	334k	335k	336k	337k
Statutory Paternity Pay	0k	0k	0k	0k	0k	0k	0k
Statutory Sick Pay	181k	182k	182k	182k	182k	183k	183k
Sure Start Maternity Grant	26k	26k	26k	26k	26k	26k	26k
Bereavement Support Payment	98k	98k	98k	98k	98k	99k	99k
Widowed Parent's Allowance	0k	0k	0k	0k	0k	0k	0k
Tax-Free Childcare	1,043k	1,027k	1,014k	1,009k	1,011k	1,009k	993k
Extended childcare entitlement	795k	800k	796k	797k	798k	798k	792k
Universal childcare entitlement	1,071k	1,072k	1,072k	1,073k	1,076k	1,079k	1,074k
Targeted childcare entitlement	165k	156k	154k	154k	155k	155k	150k
Childcare Offer for Wales	39k	39k	39k	39k	39k	39k	39k
Care to Learn	0k	0k	0k	0k	0k	0k	0k
Childcare Grant	0k	0k	0k	0k	0k	0k	0k
Parents' Learning Allowance	98k	98k	98k	99k	99k	99k	99k
Adult Dependants' Grant	18k	18k	12k	12k	12k	12k	12k
Travel Grant	0k	0k	0k	0k	0k	0k	0k
Disabled Students' Allowance	suppressed	suppressed	suppressed	suppressed	suppressed	suppressed	suppressed
16 to 19 Bursary Fund	0k	0k	0k	0k	0k	0k	0k
Cost-of-living support payment	0k	0k	0k	0k	0k	0k	0k
Energy Bills Rebate	0k	0k	0k	0k	0k	0k	0k
Household Energy Payment	0k	21,065k	0k	0k	0k	0k	0k
Energy Price Guarantee subsidy	0k	0k	0k	0k	0k	0k	0k
Basic income	0k	0k	0k	0k	0k	0k	0k
Disability basic income	0k	0k	0k	0k	0k	0k	0k

Government balance, each component counted once: head levels

Measure (head)	2025-26	2026-27	2027-28	2028-29	2029-30	2030-31	2031-32
Government receipts, each component once	£892.00bn	£934.66bn	£980.50bn	£1,015.93bn	£1,054.24bn	£1,091.56bn	£1,124.89bn
Government spending	£528.93bn †	£544.94bn †	£549.99bn †	£558.68bn †	£566.30bn †	£575.00bn †	£582.59bn †
Government balance, each receipt once	£363.07bn †	£389.72bn †	£430.51bn †	£457.24bn †	£487.94bn †	£516.56bn †	£542.31bn †
Benefits in household_benefits but not in gov_spending	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn	£0.00bn

Model totals: head levels

Measure (head)	2025-26	2026-27	2027-28	2028-29	2029-30	2030-31	2031-32
gov_tax	£892.00bn	£934.66bn	£980.50bn	£1,015.93bn	£1,054.24bn	£1,091.56bn	£1,124.89bn
household_tax	£491.97bn	£520.41bn	£551.21bn	£576.00bn	£601.00bn	£626.69bn	£648.42bn
pre_budget_change_household_tax	£484.15bn	£512.28bn	£542.82bn	£566.95bn	£591.72bn	£617.16bn	£638.61bn
gov_spending	£528.93bn †	£544.94bn †	£549.99bn †	£558.68bn †	£566.30bn †	£575.00bn †	£582.59bn †
household_benefits	£528.93bn †	£544.94bn †	£549.99bn †	£558.68bn †	£566.30bn †	£575.00bn †	£582.59bn †
gov_balance	£363.07bn †	£389.72bn †	£430.51bn †	£457.24bn †	£487.94bn †	£516.56bn †	£542.31bn †

Household income totals: head levels

Measure (head)	2025-26	2026-27	2027-28	2028-29	2029-30	2030-31	2031-32
Household market income	£1,637.96bn	£1,702.77bn	£1,757.35bn	£1,806.41bn	£1,855.97bn	£1,912.43bn	£1,970.44bn
Household net income	£1,636.24bn †	£1,687.10bn †	£1,714.68bn †	£1,746.67bn †	£1,777.79bn †	£1,816.07bn †	£1,858.68bn †
Household net income (HBAI definition)	£1,449.13bn	£1,499.11bn	£1,530.09bn	£1,564.35bn	£1,596.99bn	£1,634.64bn	£1,675.60bn

Population: head levels

Measure (head)	2025-26	2026-27	2027-28	2028-29	2029-30	2030-31	2031-32
People	69,245k	69,383k	69,473k	69,592k	69,738k	69,912k	70,080k
Benefit units	35,110k	35,181k	35,226k	35,286k	35,360k	35,449k	35,534k
Households	31,046k	31,108k	31,149k	31,201k	31,267k	31,345k	31,420k

Poverty rates: head levels

Measure (head)	2025-26	2026-27	2027-28	2028-29	2029-30	2030-31	2031-32
Absolute poverty, before housing costs: everyone	16.3%	15.5%	16.4%	16.3%	16.5%	16.5%	16.6%
Absolute poverty, before housing costs: children	24.7%	22.1%	23.3%	22.9%	23.1%	23.2%	23.5%
Absolute poverty, before housing costs: working-age adults	14.1%	13.8%	14.7%	14.7%	14.8%	14.8%	15.0%
Absolute poverty, before housing costs: pensioners	13.7%	13.4%	14.0%	13.8%	14.0%	14.0%	13.9%
Absolute poverty, after housing costs: everyone	21.6%	21.1%	22.0%	22.6%	22.9%	23.1%	23.5%
Absolute poverty, after housing costs: children	33.3%	31.3%	32.3%	32.5%	32.9%	33.4%	34.2%
Absolute poverty, after housing costs: working-age adults	19.9%	19.8%	20.8%	21.6%	21.9%	22.0%	22.3%
Absolute poverty, after housing costs: pensioners	12.7%	12.4%	13.2%	13.2%	13.3%	13.4%	13.6%
Relative poverty, before housing costs: everyone	17.0%	16.0%	16.4%	16.3%	16.4%	16.3%	16.6%
Relative poverty, before housing costs: children	25.9%	22.9%	23.3%	22.9%	23.0%	22.9%	23.5%
Relative poverty, before housing costs: working-age adults	14.5%	14.1%	14.6%	14.7%	14.7%	14.7%	15.0%
Relative poverty, before housing costs: pensioners	14.5%	14.1%	14.0%	13.8%	13.8%	13.9%	13.9%
Relative poverty, after housing costs: everyone	21.5%	21.0%	21.2%	21.3%	21.3%	21.5%	21.7%
Relative poverty, after housing costs: children	33.1%	31.1%	31.1%	31.0%	31.1%	31.2%	31.8%
Relative poverty, after housing costs: working-age adults	19.9%	19.8%	20.2%	20.4%	20.5%	20.6%	20.8%
Relative poverty, after housing costs: pensioners	12.5%	12.4%	12.2%	11.8%	11.7%	11.8%	12.1%

People in poverty: head levels

Measure (head)	2025-26	2026-27	2027-28	2028-29	2029-30	2030-31	2031-32
Absolute poverty, before housing costs: everyone	11,277k	10,784k	11,408k	11,373k	11,482k	11,521k	11,657k
Absolute poverty, before housing costs: children	3,688k	3,314k	3,496k	3,445k	3,480k	3,502k	3,549k
Absolute poverty, before housing costs: working-age adults	5,965k	5,895k	6,311k	6,366k	6,423k	6,434k	6,524k
Absolute poverty, before housing costs: pensioners	1,624k	1,575k	1,601k	1,562k	1,579k	1,585k	1,584k
Absolute poverty, after housing costs: everyone	14,944k	14,607k	15,318k	15,729k	15,946k	16,150k	16,440k
Absolute poverty, after housing costs: children	4,975k	4,682k	4,837k	4,888k	4,945k	5,040k	5,179k
Absolute poverty, after housing costs: working-age adults	8,463k	8,465k	8,976k	9,348k	9,496k	9,588k	9,715k
Absolute poverty, after housing costs: pensioners	1,506k	1,461k	1,506k	1,494k	1,506k	1,522k	1,546k
Relative poverty, before housing costs: everyone	11,750k	11,088k	11,394k	11,363k	11,422k	11,423k	11,657k
Relative poverty, before housing costs: children	3,872k	3,423k	3,496k	3,443k	3,466k	3,454k	3,549k
Relative poverty, before housing costs: working-age adults	6,159k	6,014k	6,304k	6,361k	6,392k	6,393k	6,524k
Relative poverty, before housing costs: pensioners	1,719k	1,651k	1,594k	1,560k	1,564k	1,576k	1,584k
Relative poverty, after housing costs: everyone	14,864k	14,560k	14,740k	14,811k	14,883k	15,023k	15,241k
Relative poverty, after housing costs: children	4,944k	4,660k	4,660k	4,662k	4,679k	4,707k	4,805k
Relative poverty, after housing costs: working-age adults	8,431k	8,444k	8,687k	8,823k	8,880k	8,974k	9,067k
Relative poverty, after housing costs: pensioners	1,489k	1,456k	1,393k	1,327k	1,325k	1,342k	1,369k

Inequality: head levels

Measure (head)	2025-26	2026-27	2027-28	2028-29	2029-30	2030-31	2031-32
Gini coefficient, equivalised HBAI income before housing costs	0.3078	0.3051	0.3057	0.3056	0.3061	0.3067	0.3083

Mean household net income in each side's own deciles: head levels

Measure (head)	2025-26	2026-27	2027-28	2028-29	2029-30	2030-31	2031-32
Decile 1: mean household_net_income per household	£17,681 †	£18,010 †	£17,918 †	£18,160 †	£18,301 †	£18,547 †	£18,732 †
Decile 2: mean household_net_income per household	£27,942 †	£29,024 †	£28,623 †	£29,004 †	£29,287 †	£29,699 †	£30,089 †
Decile 3: mean household_net_income per household	£34,316 †	£35,426 †	£36,075 †	£36,523 †	£36,995 †	£37,682 †	£38,154 †
Decile 4: mean household_net_income per household	£38,934 †	£40,687 †	£41,716 †	£42,770 †	£43,423 †	£44,111 †	£44,446 †
Decile 5: mean household_net_income per household	£43,235 †	£45,555 †	£46,034 †	£46,930 †	£47,714 †	£48,578 †	£50,274 †
Decile 6: mean household_net_income per household	£47,931 †	£49,240 †	£50,932 †	£51,984 †	£52,963 †	£53,976 †	£54,714 †
Decile 7: mean household_net_income per household	£55,659 †	£56,577 †	£57,445 †	£57,649 †	£58,750 †	£59,668 †	£61,096 †
Decile 8: mean household_net_income per household	£68,784 †	£70,805 †	£71,866 †	£73,514 †	£73,888 †	£75,324 †	£77,180 †
Decile 9: mean household_net_income per household	£78,889 †	£81,012 †	£80,859 †	£82,645 †	£85,463 †	£86,945 †	£89,508 †
Decile 10: mean household_net_income per household	£116,861 †	£120,160 †	£124,545 †	£126,419 †	£125,752 †	£128,367 †	£130,693 †

Standard reform costings (change in gov_balance): head levels

Measure (head)	2025-26	2026-27	2027-28	2028-29	2029-30	2030-31	2031-32
Raise basic rate by 1pp	£6.41bn	£6.66bn	£6.63bn	£6.85bn	£7.03bn	£7.25bn	£7.49bn
Raise higher rate by 1pp	£3.61bn	£3.87bn	£4.00bn	£4.22bn	£4.44bn	£4.71bn	£4.83bn
Raise personal allowance by ~800GBP/year	£-3.81bn	£-3.93bn	£-3.99bn	£-4.05bn	£-4.11bn	£-4.24bn	£-1.95bn
Raise child benefit by 25GBP/week per additional child	£-1.99bn	£-1.75bn	£-1.55bn	£-1.38bn	£-1.30bn	£-1.18bn	£-1.07bn
Reduce Universal Credit taper rate to 20%	£-20.77bn	£-21.32bn	£-21.75bn	£-22.00bn	£-22.35bn	£-22.75bn	£-22.94bn
Raise Class 1 main employee NICs rate to 10%	£10.89bn	£11.30bn	£11.71bn	£12.01bn	£12.31bn	£12.62bn	£13.00bn
Raise VAT standard rate by 2pp	£24.89bn	£25.71bn	£26.63bn	£27.24bn	£27.87bn	£28.50bn	£29.14bn
Raise additional rate by 3pp	£2.90bn	£3.15bn	£3.22bn	£3.41bn	£3.61bn	£3.85bn	£4.14bn
Raise the Universal Credit standard allowance by 10%	£-3.06bn	£-3.22bn	£-3.30bn	£-3.39bn	£-3.48bn	£-3.53bn	£-3.54bn
Raise the State Pension by 10%	£-7.76bn	£-7.99bn	£-8.22bn	£-8.44bn	£-8.79bn	£-8.52bn	£-8.86bn

Standard reforms: change in each reform's target: head levels

Measure (head)	2025-26	2026-27	2027-28	2028-29	2029-30	2030-31	2031-32
Raise basic rate by 1pp: change in income_tax	£6.55bn	£6.86bn	£6.79bn	£7.00bn	£7.20bn	£7.44bn	£7.66bn
Raise higher rate by 1pp: change in income_tax	£3.61bn	£3.92bn	£4.01bn	£4.23bn	£4.45bn	£4.72bn	£4.84bn
Raise personal allowance by ~800GBP/year: change in income_tax	£-3.93bn	£-4.07bn	£-4.13bn	£-4.18bn	£-4.22bn	£-4.40bn	£-1.75bn
Raise child benefit by 25GBP/week per additional child: change in child_benefit	£2.33bn	£2.14bn	£1.94bn	£1.76bn	£1.65bn	£1.52bn	£1.40bn
Reduce Universal Credit taper rate to 20%: change in universal_credit	£20.74bn	£21.31bn	£21.79bn	£22.05bn	£22.37bn	£22.78bn	£22.99bn
Raise Class 1 main employee NICs rate to 10%: change in national_insurance	£11.15bn	£11.63bn	£12.00bn	£12.29bn	£12.61bn	£12.94bn	£13.31bn
Raise VAT standard rate by 2pp: change in vat	£24.69bn	£25.51bn	£26.42bn	£27.03bn	£27.65bn	£28.28bn	£28.91bn
Raise additional rate by 3pp: change in income_tax	£2.90bn	£3.15bn	£3.22bn	£3.42bn	£3.62bn	£3.86bn	£4.12bn
Raise the Universal Credit standard allowance by 10%: change in universal_credit	£3.06bn	£3.22bn	£3.32bn	£3.41bn	£3.47bn	£3.53bn	£3.55bn
Raise the State Pension by 10%: change in state_pension	£10.68bn	£11.17bn	£11.28bn	£11.60bn	£12.03bn	£12.46bn	£12.96bn

[juaristi22]

Review status: COMPLETE at 5a784a7e926d4bc5b1471770ae67d4f96f139140. No findings or material evidence gaps.

Independent code/test and policy/source review covered the stored UC health and PIP draws, student-loan take-up, supplied-input precedence, provenance/cache/lifecycle checks and Core Dataset routing. The change introduces allocation inputs rather than new statutory rules.

Validation: 202/202 focused repository tests passed on the lock-matched Core 3.34.1 environment, plus one synthetic final-output/order check. The stored UC draw changes LCWRA, final Universal Credit and household net income by the same £2,550.48; reversing calculation order gives identical results. The unchanged #2873 randomness guard was checked byte-for-byte against its prior reviewed head; its earlier 384 passes were reused, not rerun or added to the 202 count. All 20 hosted checks currently pass at this exact head.

Equivalence remains conditional on the supplied reference decisions and covered thresholds. This review does not certify producer calibration, private datasets, population effects, arbitrary-share float64 equivalence or the author's full dual-Core-version/mutation totals. The disclosed shadowed-input/carry-ranking changes and seeded fallback boundary remain explicit.

Approval withheld: this PR is still a draft and its description requires #2873 to land first. The completed review can be reused when readiness, parent integration and exact-head checks are reassessed.