UK #1095 A/B fixes: the SPI age band (uk-data#628), households' HRAD from Table 8a receipts, and the SPI pay floor (uk-data#629)

changelog.d/1095-hrad-nil-band-receipts.changed.md

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+The UK property purchases stage allocates households' additional-dwelling (HRAD) purchases at or below GBP 250,000 from HMRC's Table 8a receipts instead of individuals' share of all transactions (microcosm#1095). The residential nil-rate band was GBP 250,000 for all of 2024-25, so a purchase in that band owes no standard-rate SDLT and other buyers' receipts there are surcharge: at Table 6b's gross HRAD receipts per transaction and per pound, their GBP 265m is about 48,100 HRAD transactions and GBP 7.05bn, against the 13,400 transactions the all-band share left them. Households take the rest of the band; above it they keep uk-data#573's shares, which probably still overstate them, since the standard rates make up most receipts there. Households' 2024-25 target falls from 186,589 transactions and GBP 68.81bn to 151,928 and GBP 63.71bn, both above uk-data#573's lower bounds, and the lowest band's share of their purchases from 54% to 43%. The stage's derivation records the nil-band receipts, the implied HRAD and its shares.

changelog.d/1095-spi-forest-age-band.changed.md

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+The UK SPI income stage's stage-1 tape and reference forests now read the SPI age band, not an age (uk-data#628). The 2022-23 SPI tape gives age only as a band (AGERANGE), so the age the stage draws for each donor inside its band carried no income pattern: the forest learned none, and FRS twins in one band were drawn from conditionals that differed only by that noise. The predictor `spi_age_band` is the tape's own AGERANGE code, with composite records (-1) as a band of their own, and for a frame person the band of their whole-year age. It is one-hot encoded, so the composites, the tape's high-income amalgams, are a category of their own rather than the neighbours of 16-24 on an ordinal scale; `at_or_over_spa` still carries the State Pension split inside the 65-74 band. The cross-fit fold cells key on the band too, since they key on the predictor values. The drawn donor ages are kept for the band pools' State Pension side. The stage receipt's `stage1_age_predictor` names the rule.

changelog.d/1095-uk-carers-allowance-after-salary-sacrifice.changed.md

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+The UK Carer's Allowance take-up stage now runs after `salary_sacrifice`, so its earnings test reads the pay that salary sacrifice converts into pension contributions (microcosm#1095 B5). That also puts it after the CGT stages' copies, so its draws are keyed on lineage: a member of a CGT support copy, incidence clone or residential arm draws as the member at the same rank of the household it copies (`lineage_roots`), and the balanced placement takes a source and its copies in one stratum as one record of their joint weight (`lineage_balanced_positions`), so the two claim together as before. Original rows keep their draws. The stage spec, the coverage manifest and the H2 fixture follow.

changelog.d/1095-uk-uc-take-up-gate-pools.changed.md

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+The UK Universal Credit take-up stage gate (`uk_stage_uc_take_up`) gives the reachable pools a tolerance of their own, `maximum_reachable_pool_deviation`, beside the family type's caseload's `maximum_caseload_deviation` (Vahid's review of #1426). Both stay at 0.055 of DWP's count. With #1428's pool joining, every family type ends closer to DWP's count after the redraw than before it, the SPI employment pay floor (uk-data#629) included, so the caseload needs no wider allowance (María's ruling of 2026-11-02). The contract re-pins the gate battery's policy, manifest and fingerprint digests and the release certification's spine part.

changelog.d/1418-spi-donor-savings-rebase.changed.md

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+The SPI income stage now rebases the 2022-23 tape's interest and other income to HMRC's published 2023-24 Table 3.7 amounts band by band (the published rows are vendored as `uk/hmrc_spi_table_3_7_savings_rows.json`), then carries both to the frame's year on the OBR's savings income growth (October 2026 EFO, Table 4.5), the path the Table 3.7 band targets take (#1418 savings follow-up, #1428). Before, each column moved by its engine index from 2022 to 2024: other income by GDP per head (x1.09) where SPI's own other income grew x1.65 in the single year to 2023-24, and interest by ONS household interest (x2.27) where SPI's grew x2.69 in that year. The frame then carried about 70 percent of the Table 3.7 savings rows at design weights, and the solve met them by stretching the weights of the few households that carry them. Each band's factor is the published amount over the FACT-weighted amount of the tape's taxpayers in the band, as Table 3.7 counts taxpayers only. The tape is banded once on its income moved to 2023-24, each income leaf at its own factor and each rebased column at its factor over all bands, so the band-edge migration its consumers re-band on uprated income is counted once; a record whose band's factor differs from that of all bands can still sit across an edge on its rebased income. A taxpayer is a record the tape flags (TAXPAYER 1) or one whose income crosses the Personal Allowance by 2023-24, so a saver who becomes a taxpayer counts once; a flagged taxpayer below the first band sits in it (note 8), and any other record takes the factor of all bands. A band too thin to gross (under a tenth of its published amount) takes the factor of all bands, a column whose tape does not gross to the published amounts is left as it is and grows on its engine index from 2022-23, and a tape whose TAXPAYER codes are not 1 or 2 is refused. On the tape, the £1m-and-over band's other income outweighs its interest, as in the published table, so the rebase also undoes the split the two indices had flipped.

changelog.d/1428-dwp-jsa-income-based.added.md

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+The national calibration binds DWP's income-based Jobseeker's Allowance spending, `dwp.jsa.amount_income_based` (benefit expenditure and caseload tables, Spring Forecast 2026), at the calendar-2025 window of the fiscal years, as the pension-age Housing Benefit row is (#1428; María's ruling of 2026-10-31). Income-based JSA closes with the move to Universal Credit: £91.0m in FY2024-25 and under £1m from FY2025-26. Without the split, the calibration meets OBR's total JSA by scaling income-based reporters together with contributory claimants, far past DWP's income-based spending.

changelog.d/1428-frs-other-income-definitions.changed.md

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+FRS rows now book NS&I income on SPI's definitions (#1428). NS&I Direct Saver and the other NS&I and bank products go to `savings_interest_income`, because SPI has counted all interest paid gross or net as bank interest since 2016-17 (Table 3.7 note 4); gilts stay in `other_investment_income`. Income from an annuity not bought with pension funds or from a trust or covenant (FRS PENTYPE 4 and 5) stays in `private_pension_income`, where policyengine-uk's means tests (Pension Credit, Universal Credit, Housing Benefit, Council Tax Reduction, Income Support), household income and tax read it. Its part is stored in a new calibration-only descriptor, `annuity_and_trust_income`, and SPI Table 3.7's other-income rows read `other_investment_income_spi_concept`: the engine's other income plus that share of the engine's private pension, as the table counts both payments as other income (note 6). A row the SPI stage draws holds the tape's pension, which excludes them, so its descriptor is zero. The FRS spine now refuses a pension tab without PENTYPE.

changelog.d/1428-isa-fit-weight-records.fixed.md

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+The ISA subscriptions stage no longer declares an empty list of fit-weight records (#1428). It fits no model, but the release-cut weights audit read its empty list as a fitting stage that recorded nothing, so every national certified after #1421 failed `uk_weights_audit`.

changelog.d/1428-spi-employment-by-self-employment-band.added.md

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+The national calibration binds SPI 2023-24 Table 3.10's individuals with employment income by self-employment band, `hmrc.spi.employment_income.count_by_self_employment_income_band`, over the eight bands from £1 to £10,000 that the self-employment counts and amounts already bind (#1418; María's choice of 2026-10-30). With the self-employment counts alone, the solve could meet each band with traders who have no pay, while in Table 3.10 more than half of the traders below £3,000 also have employment income; an employee's side profit is taxed at their marginal rate, so the mix of small traders decides what the Budget's trading allowance measures cost. Each person with pay or company car benefits over the year (`employment_income_with_benefits_in_kind_annual`, the term every HMRC employment income row reads since #1430) counts in their own self-employment band, taxpayer or not. Table 3.10's column is wider, income assessed under ITEPA 2003 plus other miscellaneous income, so like Table 3.6's employment rows the binding leaves out miscellaneous income and the contributory benefits; benefits in kind count on SPI rows, whose pay is the tape's PAY + EPB + TAXTERM, and the company car and car fuel benefits on every row. Counts grow to 2025 with HMRC's projected growth of all taxpayers (Income Tax liabilities statistics Table 2.5), as the self-employment counts do, and the zero band and the bands from £10,000 are signed out row by row.

changelog.d/1428-spi-gift-anchor.changed.md

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+The SPI income stage anchors the drawn copies' Gift Aid and charitable investment gifts to the SPI tape's own weighted totals (#1428; María's ruling of 2026-10-31). Both are sparse leaves that the stage-1 chain draws after, and conditioned on, the income leaves, so a change to the savings draws reshuffles which few donors' gifts the copies draw. Each column's total over the drawn copies, at the stage's household weights, is scaled to the tape's FACT-weighted total. A column that the tape or the copies carry none of is left as drawn. The scaling fixes the totals, not how concentrated each column is. The stage evidence records each column's factor, never a total or a count.

changelog.d/1428-spi-other-income-analogue.changed.md

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+The SPI stage-1 transport now locates each copy's other-income draw at its FRS twin's own other income (gilt interest), as it does for the other investment leaves, instead of an identity uniform that ignored the twin's holdings (#1428).

changelog.d/1428-trading-allowance-receipts.added.md

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+A new last spine stage, `trading_allowance_receipts`, stores the self-employed's gross receipts (`self_employment_gross_receipts`), so policyengine-uk applies the trading allowance against receipts as the law does (#1428; María's choice of 2026-10-31). Neither the FRS nor the SPI tape records turnover. Without receipts the engine relieved profits up to the allowance in full and nothing above it, so a rise in the allowance missed its main base: traders who already claim the £1,000 allowance against larger receipts. Under current law a claimant's receipts are their profit plus £1,000 exactly. Each trader with a positive profit is flagged as a claimant with probability 0.72 for profits up to £4,500, 0.14 from £4,500 to £9,000 and none above, drawn on their own `person_id`. A claimant's receipts are their profit plus £1,000; any other trader's are their profit plus £3,000, expenses at the raised allowance, since the costing books traders who switch to the allowance as behaviour. The rates are calibrated to HMRC's policy paper (about 400,000 taxpayers with a lower bill, by about £380 on average), measured on policyengine-uk for the national from 9f70c71e7, until HMRC publishes claimant counts; they drift with each national, so #1439 re-measures them after each build. Every trader with a positive profit is treated as filing, as the Table 3.10 counts the calibration binds are of filers, so a profit of £1,000 or less is now taxed where the engine used to relieve it in full. Two limits remain until policyengine-uk#2765 lets the stage store the claim status itself (#1439). A claimant's £1,000 grows with the mixed income index while the allowance is nominal, so the raise relieves £1,932 more in 2027-28, falling to £1,758 by 2031-32. The other traders' stored £3,000 grows the same way, so allowances above £3,000 are mis-scored. `self_employment_gross_receipts` leaves the register of engine inputs left at their default and joins the export surface's allowed columns. The stage spec and schema, the graph and kernel wiring, the spine build, the coverage manifest, the H2 fixture and the data contract's gate digests follow.

changelog.d/1428-uc-take-up-passes-unmet-gaps.changed.md

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+The Universal Credit take-up stage now passes the gap of a pool that cannot meet DWP's count to its neighbouring pools, so each family type's caseload lands on DWP's wherever its entitled units allow (#1428; María's rulings of 2026-10-31 and 2026-11-01). The stage pools adjacent award bands within a family type until they rest on enough sources. A pool can't meet DWP's count when its reporters' and other undrawn units' expected claims already exceed it, or when the count exceeds every entitled unit. Such a pool used to keep its clipped rate, which left the family type's caseload off DWP's by the gap, and which bands fell short moved with small upstream changes. Now such a pool is held at its clip and its gap passes on. A shortfall and an excess elsewhere in the family type offset first. What remains goes to the other pools, nearest first, the one with more room first at equal distance and the lower band on a tie, each taking what its room allows. Every band keeps its own rate, so no band's drawn units claim against its own count to meet another's. The stage spec, the coverage manifest, the H2 fixture and the data contract's gate digests follow.

changelog.d/uk-spi-employment-pay-floor.fixed.md

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+The UK SPI income stage now gives drawn employees current pay consistent with their twin's hours, and keeps the SPI tape's pay as their year of pay (uk-data#629). Stage 1 draws annual tape pay on age, sex, region and the bridge predictors but not on hours, and the tape holds part-year workers, so a copy whose FRS twin reports usual hours in an employee job could draw a year's pay below what those hours earn at the minimum wage and fail the minimum-income tests of the 30 hours' childcare offer, Tax-Free Childcare and the benefit cap more often than FRS rows. A new `floor_spi_employment_pay_at_minimum_wage` operation of `hmrc_spi_income_spine` lifts the drawn `hmrc_spi_pay` leaf to the twin's usual weekly hours (`hours_worked` read back at 52) times 52 weeks times the lower of policyengine-uk's `gov.hmrc.minimum_wage.non_apprentice` rate for the twin's age, read as the engine reads the build year (2024-25: £11.44 from 21, £8.60 from 18, £6.40 below), and the twin's own hourly pay, so no copy is held to a higher hourly rate than the FRS person it copies. The floored pay is the row's current pay; its `employment_income_annual_share` becomes its unfloored over its floored employment income, so the annual measures, which the HMRC income rows read, still read the tape's pay: low tape pay is read as part of a year at the floored rate. The operation runs after the stage-1 draw, the band-donor resample and the State Pension leaf guard, and before `employment_income` is derived from the leaves and stage 2 conditions on it, so the pension contributions (#1332's twin employer rate now applies to the floored pay) and every later stage read the floored current pay; the transport receipt keeps the unfloored draws' uniforms. It touches only drawn recipients other than reserved band carriers, whose twin has an employee main job, no trade and usual hours, and whose drawn pay is positive; FRS rows are never modified. Tape PAY is taxable pay, net of net-pay pension contributions and salary sacrifice, while the minimum wage binds gross pay: PAY alone is compared with the gross minimum, since it is the leaf of the engine's gross `employment_income` input. The stage evidence gains an `employment_pay_floor` receipt with eligible and floored source households (rounded), weighted people, the weighted share floored, the weighted mean uplift and the amount added, and an hourly-pay check: the weighted shares of the drawn employees below the minimum wage for their age before and after the floor beside the FRS employees' share, and the eligible rows still below their floor; every figure on one to nine source households, or beside a side on one to nine, is "<10". A new release-blocking stage gate, `uk_stage_hmrc_spi_income_spine_hourly_pay`, refuses a spine where an eligible drawn employee stays below its floor or where, after the floor, drawn employees sit below the minimum wage more often than FRS employees by more than two points; its details give verdicts only. The gate joins the spine gate scope, so spines saved before it no longer match a build's battery.

docs/uk-income-anchors-280.md

@@ -80,8 +80,10 @@ membership carries the uprated value with its receipt.
   others take `policyengine_uk_parameter:<path>`, the ratio of the pinned
   engine's parameter between 1 January of the fact's opening year and 1
   January of the calibration year, the instants the SPI donor rebasing already
-  uses: dividends `obr.per_capita.gdp`. Savings interest takes two legs
-  (microcosm#1095): `ons.household_interest_income`, the index of its
+  uses: dividends `obr.per_capita.gdp`. Savings interest outside SPI Table
+  3.7's rows takes two legs (microcosm#1095); Table 3.7's interest and other
+  income rows take the OBR's savings income path from 2023-24 instead, as the
+  next paragraph says (microcosm#1418): `ons.household_interest_income`, the index of its
   history, to the dataset's year, then `obr.per_capita.gdp`, the index the
   engine's dataset projection applies, to the calibration year (1.1420 x
   1.0474 = 1.1961 on the pinned engine values; 1.0438 and 1.1920 before
@@ -96,6 +98,28 @@ membership carries the uprated value with its receipt.
   by `tools/pin_uk_uprating_engine_values.py`, whose `--check` refuses drift), so
   it runs and reproduces without policyengine-uk; a `requires_uk` test holds the
   pins in lockstep with the installed engine, and an engine bump re-runs the tool.
+
+  The SPI donors reach the frame's year apart from these indices for interest
+  and other income (microcosm#1418 savings follow-up). The income stage first
+  scales each donor's two columns to HMRC's published 2023-24 Table 3.7 amounts
+  in its band of total income (`spi_income.rebase_spi_donor_savings`, the rows
+  vendored as `uk/hmrc_spi_table_3_7_savings_rows.json`), then grows them on the
+  OBR's savings income path the Table 3.7 targets take
+  (`hmrc_uprating.uk_obr_savings_income_level`). Each band's factor is the
+  published amount over the FACT-weighted amount of the tape's taxpayers in
+  the band, as Table 3.7 counts taxpayers only (microcosm#1428). The tape is
+  banded once on its income moved to 2023-24, each income leaf at its own
+  factor and each rebased column at its factor over all bands, so the
+  band-edge migration the consumers re-band on uprated income is counted
+  once. A record whose band's factor differs from that of all bands can still
+  sit across an edge on its rebased income. A taxpayer is a record the tape flags (TAXPAYER 1) or one whose income
+  crosses the Personal Allowance by 2023-24; a flagged taxpayer below the first
+  band sits in it (note 8); any other record takes the factor of all bands. A
+  band the tape carries none of is left as it is, a band whose tape amount is
+  under a tenth of its published amount takes the factor of all bands, and a
+  column whose tape does not gross to the published amounts is left as it is
+  and grows on its engine index from 2022-23. From the frame's year on, the
+  engine projects the two columns on their own indices.
 - Count rows: `hmrc.itl_2026.taxpayer_count_growth_by_total_income_band`, HMRC's
   own projected growth in Income Tax payers for the Table 2.5 band that contains
   the SPI band (Income Tax liabilities statistics, July 2026), as the
@@ -405,8 +429,9 @@ fold differs from its twin's, and a reference whose sign classes differ from
 the tape forest's on any located target. One difference between the two
 forests remains: the reference locates a leaf given the twin's observed
 earlier analogue leaves, while the tape forest draws it given every earlier
-output, the three identity-uniform leaves (`other_investment_income`,
-`gift_aid`, `charitable_investment_gifts`) included, so a located quantile is
+output, the two identity-uniform leaves (`gift_aid`,
+`charitable_investment_gifts`) included, since `other_investment_income` has
+located at the twin's own other income from microcosm#1428, so a located quantile is
 read off a conditional those identity draws also shape; pay, which follows
 them in the chain, has the weakest rank fidelity, and moving the analogue
 targets ahead of the identity leaves is the follow-up to measure. Because the