Sources verified for 2020/21

Verified against

Added for pre-2022-23 carry-forward (live-case-test F1). HMRC Income Tax rates 2020-21 (gov.uk): PA £12,500, basic-rate band £37,500 (HRT £50,000), additional-rate threshold £150,000, rates 20/40/45; PSA £1,000/£500/£0; starting-rate band £5,000 @ 0%; dividend rates 7.5/32.5/38.1 + £2,000 allowance; trust 45% / dividend-trust 38.1%; CGT AEA £12,300, rates 10/20 (non-property); ISA £20,000. AA fields (PTM057100, FA 2020 effective 2020-21 — the year the taper threshold rose to £200k/£240k and the floor dropped to £4k): standard AA £40,000, taper threshold income £200,000, taper adjusted income £240,000, taper floor £4,000, taper £1/£2; MPAA £4,000 (PTM056510, since 2017-18); AA charge marginal-rate default 45%. priorSeptemberCPI = 1.7% (Sept 2019, ONS D7G7) for DB-PIA opening revaluation (FA 2004 s.235(3) / PTM053301 / ADR-027). LSA/LSDBA = 0 (LTA regime in force 2020-21). HICBC £50,000 threshold / 1% per £100; Child Benefit £21.05 eldest + £13.95 additional weekly (historical DWP 2020-21 — operator to confirm). Non-AA fields are best-effort for the rare historical single-year calc; the load-bearing use is prior-year carry-forward taper, which reads only the AA/taper fields.; trust standard rate band GBP1,000 first slice at non-trust rates, GBP200 floor per settlement (ITA 2007 ss.491-492, in force through 2023-24); W7/ADR-051 (2026-07-01): FA 2004 s.227ZA(1)(b) MPAA alternative chargeable-amount gate (money-purchase input sub-total must exceed the MPAA), s.228A(8) carry-forward substitution in an MPAA year (PTM055100), s.228ZA(2) annual-allowance taper reduction floors to the nearest whole GBP1 (not the nearest penny); W9/ADR-049 (2026-07-01): pre-2024 LSA/LSDBA transitional previously-used amount revalues to the GBP1,073,100 basis using the exact s.219(4)/(5) fraction at the historic BCE date (FA 2024 Sch 9 para 129(4A)), not the 2dp-percent shortcut; SIH_pre75 default-side LSA deduction is 25% of the revalued amount, not zero (FA 2024 Sch 9 para 125(3)). W1/D1-D3 (2026-07-01): ITA 2007 s.12/s.23/s.16 SRB erosion base corrected to the ACTUAL (post-taper) personal allowance (not the untapered config figure); PSA (ss.12A-12B, s.10(3A), s.58(1) Steps 2-3) now tested against taxable income and the EXTENDED higher/additional-rate limits (Gift Aid/RAS band extension + s.58(1) Steps 2-3 ANI default), with the additional-rate test strict '>' rather than '>='. W2/A1/A4 (2026-07-01): ITTOIA 2005 s.531(1) express carve-out — the s.530(1) deemed basic-rate credit now applies within the top-slicing relief calculation for offshore bonds too (not just onshore); s.530(3)-(5) restricts the credit (both bond types) to the gain/slice less any unused personal allowance, replacing the previous flat 20% x gain formula. W3/A2 (2026-07-01): ITTOIA 2005 s.536(1) Step 1 / IPTM7560 - N for top-slicing relief is a pure pass-through of complete 12-month periods from policy commencement to the event (no same-tax-year-straddle +1); ADR-048 supersedes ADR-012, whose N+1 reading had no statutory basis.. Calc-correctness remediation 2026-07-01 (W14, findings F1/IC-3, no numeric config value changed): FA 2004 s.233(1)(b) — the salary-sacrifice AA test now counts the full employer contribution reaching the pension (sacrifice + any employer-NI passback), not the raw sacrifice; FA 2004 s.228ZA(4)/(5)/PTM057100 — the pension advanced form's taper-toggle-OFF earnings proxy now always applies the salary-sacrifice add-back to both threshold and adjusted income. W8/B3 (2026-07-02, no numeric value changed): FA 2004 s.228A(5)(b)/(6)/(7) - carry-forward now runs a sequential intra-window set-off ledger across the supplied prior-year evidence: an intervening year's own breach (that year's PIA exceeding that year's own applicable AA) is automatically covered by carry-forward from even older years, oldest-first, BEFORE any of it can reach the target year, replacing the prior each-year-in-isolation computation.; W4/A3 successive part-surrender excess N per ITTOIA 2005 s.536(1) Step 1 second limb + IPTM7560 (N = complete insurance years since the previous calculation event; from-commencement when none or a pre-6-April-2013 foreign policy) W11/C2/C7/C8/ADR-053 (2026-07-02): FA 2024 Sch 9 para 126(1)(c) - Enhanced Protection LSDBA is the value of uncrystallised rights on 5 April 2024 (FA 2004 Sch 36 paras 12(3A)/12A via SI 2024/1012; s.212), not an unlimited sentinel; para 125(1)(c) - EP holders with a registered lump sum protection use the protected-percentage-of-5-April-2023-pot entitlement, those without use the GBP375,000 base less the 25% transitional deduction (PTM174400 Fabian GBP342,500); para 125(3A)/126(3A) - the Primary Protection transitional deduction is capped at GBP375,000 (PTM174500 Petra/Krishna); PP LSDBA = GBP1,800,000 x (1 + certificate enhancement factor); Fixed Protection 2012 LSA GBP450,000 / LSDBA GBP1,800,000 and Fixed Protection 2014 LSA GBP375,000 / LSDBA GBP1,500,000 as fixed nominal amounts, no CPI indexation (PTM174700). W6/ADR-050 (2026-07-02, no numeric config value changed): ITA 2007 s.25(2) - the personal allowance is now allocated across non-savings/savings/dividends in the way that gives the greatest reduction in liability (beneficial allocation via an exact vertex search over band/SRB/PSA/dividend-allowance breakpoints), not a fixed non-savings-first order; savings and dividends remain UK-rate under both the rUK and Scotland regimes; HMRC SA Exclusions 140/142 mean HMRC own online SA calculator may show a higher figure for the affected shapes (the statute is authoritative). FA 2026 makes non-savings-first PA allocation mandatory from 2027-28 - loader TODO gates the optimiser off for that year. W16/IC-17 (2026-07-02, additive/opt-in, no numeric config value changed): wrapper-comparison exit-year income - an optional exitYearOtherIncome sets the marginal rate for the two EXIT-only computations (the bond chargeable-event top-slicing relief per ITTOIA 2005 s.535-537 and the exit-year residual GIA CGT band split per TCGA 1992), while the accumulation-year income/dividend drag and the ISA leg stay on today's income; when omitted the exit year uses otherIncome and the output is byte-identical. W12/IC-8 (ITEPA 2003 s.637S; PTM073010): a taxable LSDBA death-benefit lump-sum excess is priced on the RECIPIENT's marginal rate (recipientTaxableIncome), not the deceased's; the LSA/LSDBA excess-tax income base now prefers reduced_net_income over the adjusted_income proxy. R10/ADR-063 (2026-07-25): Scottish non-savings bands 2020-21 starter 19%/basic 20%/intermediate 21%/higher 41%/top 46%, gross boundaries GBP14,585/25,158/43,430/150,000 (gov.scot Scottish Income Tax 2020-2021: rates and bands; Scottish Rate Resolution 2020; standard PA GBP12,500). No advanced band existed before 2024-25 - the higher band runs to the top-rate threshold (ADR-063). Savings + dividends UK-wide.