Data sources
Every figure a calculator produces should be traceable to a primary source. This page lists each dataset behind the calculators: where it comes from, the date the current values took effect, how current the data is (for the monthly statistical series, the latest published month the figures run to), and — for the technically curious — how it reaches the site and what triggers an update.
A note on the status labels: Review due means a dataset is past its routine review threshold, not that any figure is wrong — for the monthly series it means a newer monthly figure is likely now published and due to be pulled in; most of the rate series change rarely and on announced dates. Provisional flags values we have published as a stop-gap (always with an on-calculator warning) while an announced change is still unsettled.
Rates and indices
Figures that change when an official body announces or publishes them. Each is updated by hand from the primary source (or by a maintained refresh script) and carries a routine review threshold.
Special Account Rate
CurrentSource: Court Funds Office (HM Courts & Tribunals Service)
Used by: Simple Interest on Damages
How this dataset is maintained
Manually curated: updated by hand when the issuing body announces a change.
Update trigger: MoJ/CFO rate announcement on GOV.UK (published as a news story since 2025 — the old 'interest rate changes' reporting page stopped updating in Dec 2024) — append a row to the JSON and repoint sourceUrl at the latest announcement.
Changes are infrequent and announced; the review threshold is a backstop. Series verified against the 9 Jan 2026 MoJ announcement (SAR 3.75% from 9 Jan 2026) in the 2 Jul 2026 review.
Bank of England base rate
CurrentSource: Bank of England (official Bank Rate history)
Used by: Simple Interest on Damages · Late Payment of Commercial Debts · Contractual and Statutory Interest · Compound Interest
How this dataset is maintained
Manually curated: updated by hand when the issuing body announces a change.
Update trigger: MPC rate decision — append a row to the JSON. The Late Payment calculator derives its statutory reference rate (base rate on 31 Dec / 30 Jun) from this same series.
Full post-2003 series re-verified row-by-row against the BoE official history in the 2 Jul 2026 review; the Dec 2025 change date was corrected from 19 to 18 Dec 2025 (BoE lists 18 Dec).
Court Funds Office basic account rate
CurrentSource: Ministry of Justice / Court Funds Office announcements (GOV.UK)
Used by: Simple Interest on Damages
How this dataset is maintained
Manually curated: updated by hand when the issuing body announces a change.
Update trigger: MoJ/CFO rate announcement on GOV.UK (published as a news story since 2025 — the old 'interest rate changes' reporting page stopped updating in Dec 2024) — append a row to the JSON and repoint sourceUrl at the latest announcement. Coverage starts 29 Apr 2022; earlier dates get a clear no-data message.
Series verified against the 9 Jan 2026 MoJ announcement (basic account 2.81% from 9 Jan 2026) in the 2 Jul 2026 review.
RPI All Items index (ONS series CHAW)
Review dueSource: Office for National Statistics, series CHAW (MM23)
Used by: Inflation & RPI
How this dataset is maintained
Script-refreshed: a maintained script re-pulls the full published series.
Update trigger: Monthly ONS RPI print (mid-month) — run scripts/refresh-rpi-data.mjs, which rewrites the JSON from the full published series.
Average Weekly Earnings index (ONS series K54L)
Review dueUsed by: Earnings Uplift (AWE)
How this dataset is maintained
Script-refreshed: a maintained script re-pulls the full published series.
Update trigger: Monthly ONS AWE release (mid-month) — run scripts/refresh-awe-data.mjs, which rewrites the JSON from the full published K54L series.
UK House Price Index (ONS / HM Land Registry)
Review dueUsed by: House Price Index (UK HPI)
How this dataset is maintained
Manually curated: updated by hand when the issuing body announces a change.
Update trigger: Monthly UK HPI release (around the third Wednesday) — re-extract the United Kingdom index and average-price columns from the ONS monthly workbook into the JSON.
Care & attendance hourly rates (NJC pay spine)
ProvisionalSource: NJC for Local Government Services pay spine, SCP 2 (SCP 3 from April 2026)
Used by: Care & Attendance
How this dataset is maintained
Manually curated: updated by hand when the issuing body announces a change.
Update trigger: Annual NJC pay settlement — update the year row; aggregate and day-aggregate rates are fixed multiples (×1.3138 / ×1.2142) of basic.
The 2026/27 row is provisional: SCP 2 was abolished from 1 Apr 2026 and the 2026/27 NJC award is unsettled; 2025/26 figures are rolled forward with an on-page warning until the award lands (see docs/CARE-RATES-NJC-2026-FINDINGS.md).
Income tax & National Insurance bands (2020/21–2026/27)
CurrentSource: HMRC rates and thresholds / Finance Acts
Used by: Tax Calculator · ET Compensation & Grossing Up · Employment Settlement Helper
How this dataset is maintained
Manually curated: updated by hand when the issuing body announces a change.
Update trigger: Budget / annual thresholds SI — add the new tax year to all three calculators (a shared tax engine is on the roadmap to collapse the copies).
2026/27 bands frozen at PA £12,570 / basic £50,270 / additional £125,140 under the fiscal-drag policy.
Vento bands (injury to feelings)
CurrentSource: Presidential Guidance (Employment Tribunals), annual Vento addendum
Used by: Vento Bands
How this dataset is maintained
Manually curated: updated by hand when the issuing body announces a change.
Update trigger: Annual Presidential addendum (effective 6 April) — add the new year's bands.
Statutory redundancy pay weekly cap
CurrentSource: Employment Rights (Increase of Limits) Order (annual SI)
Used by: Statutory Redundancy Pay
How this dataset is maintained
Manually curated: updated by hand when the issuing body announces a change.
Update trigger: Annual Increase of Limits Order (effective 6 April) — add the new year's cap.
Current cap £719/week (2025–26).
Guideline Hourly Rates
CurrentSource: Civil Justice Council / SCCO Guideline Hourly Rates
Used by: Cost Budgeting Helper · Guideline Hourly Rates
How this dataset is maintained
Manually curated: updated by hand when the issuing body announces a change.
Update trigger: Annual GHR uplift (typically January) — add the new year's bands to public/data/ghr-rates.json (canonical) and bump its lastUpdated. cost-budgeting.html still holds an inline copy to migrate post-launch. Pre-2021 rates deliberately out of scope (decision 21 May 2026).
2026 bands verified figure-for-figure against the Master of the Rolls' 1 Jan 2026 announcement (judiciary.uk) in the 2 Jul 2026 review.
Fixed publications
Reference tables that change only when the source publishes a new edition. No freshness claim is needed — the edition is the fact that matters.
ASHE occupational earnings (4-digit SOC 2020, ONS Table 14)
ProvisionalUsed by: Occupational Earnings (ASHE)
How this dataset is maintained
Fixed publication: changes only when the source publishes a new edition.
Update trigger: Annual ASHE release (provisional Oct/Nov; revised the following year) — drop the new Table 14 workbooks into docs/source-data/ASHE/ and run scripts/build-ashe-occupations.py to rewrite the JSON.
ASHE 2025 figures are PROVISIONAL (the 'PROV' ONS edition); revised figures publish ~Oct 2026. 412 four-digit SOC 2020 unit groups, full-time employees, gross pay; suppressed cells are null. Built from the ONS Excel workbooks (not on NOMIS) via scripts/build-ashe-occupations.py.
Ogden Tables 1–36 multipliers (8th edition)
Fixed publicationSource: Ogden Tables, 8th edition (Government Actuary's Department)
Used by: Multiplier Getter · Split Multipliers
How this dataset is maintained
Fixed publication: changes only when the source publishes a new edition.
Update trigger: A new Ogden edition or a change in the personal injury discount rate — re-extract the affected tables.
Date is registry-carried: the JSON's top-level keys are table numbers iterated by the calculators, so metadata fields can't be added to the file. Shared by both multiplier calculators since 30 May 2026 (verified byte-identical to the prior inline copies; 64,285-lookup regression).
Ogden Tables A–D reduction factors
Fixed publicationSource: Ogden Tables, 8th edition, Tables A–D
Used by: Multiplier Getter · Split Multipliers
How this dataset is maintained
Fixed publication: changes only when the source publishes a new edition.
Update trigger: A new Ogden edition — re-extract (936 entries).
Date registry-carried for the same reason as the multipliers file.
Judicial College Guidelines brackets (18th edition)
Fixed publicationSource: Guidelines for the Assessment of General Damages, 18th ed. (Judicial College / OUP)
Used by: JCG Brackets
Licensed content — access restricted.
How this dataset is maintained
Fixed publication: changes only when the source publishes a new edition.
Update trigger: A new JCG edition — re-extract the bracket data.
ISO 7029:2017 age-associated hearing-loss baselines
Fixed publicationSource: ISO 7029:2017 (112-row encoding)
Used by: NIHL Assessment
How this dataset is maintained
Fixed publication: changes only when the source publishes a new edition.
Update trigger: A new ISO 7029 revision — re-encode the baseline tables.
The 2017 standard was endorsed in Abbott v MOD [2026] EWHC 941 (KB) at [733(i)]; a known sign-flip typo in the published 3kHz/80yo row was corrected at encoding (see docs/NIHL-METHODS-SPEC.md). From 2 Jul 2026 the Moore pathway applies Abbott's cohort-wide 2.4 dB baseline allowance at 1–8 kHz ([733(ii)]) by default, with an on-page toggle. Open point: verify the encoded table against the 2024 corrigendum to ISO 7029:2017, which Abbott preferred.
Asbestos exposure activity catalogues (EH35 + Harries 1971)
Fixed publicationSource: HSE Guidance Note EH35 (Oct 1984) and Harries 1971 (~55 entries)
Used by: Asbestos Exposure
How this dataset is maintained
Fixed publication: changes only when the source publishes a new edition.
Update trigger: Historical documents — effectively fixed. Extend only if a further published catalogue is adopted.
HAVS tool vibration catalogue (HSE)
Fixed publicationSource: HSE hand-arm vibration guidance (18-tool catalogue incl. published low/high ranges)
Used by: Vibration (HAVS)
How this dataset is maintained
Fixed publication: changes only when the source publishes a new edition.
Update trigger: HSE guidance revision — update the tool entries.
Stopping & braking distances
Fixed publicationSource: The Highway Code (typical stopping distances, reference deceleration)
Used by: Stopping & Braking
How this dataset is maintained
Fixed publication: changes only when the source publishes a new edition.
Update trigger: Highway Code revision — update the constants.
Statutory frameworks
Logic and figures fixed by legislation, statutory instrument or rules of court. These change only when the law changes.
Personal injury discount rate (England & Wales)
Fixed publicationSource: Lord Chancellor's determination (Civil Liability Act 2018)
Used by: Multiplier Getter · Split Multipliers · Multipliers for Fixed Periods and Intervals · Swift v Carpenter
How this dataset is maintained
Statutory: changes only when legislation, an SI or a rule amendment takes effect.
Update trigger: Lord Chancellor's periodic review — update the default rate in the discount-rate pickers (the pickers already span −2% to +3%, so a new rate is selectable immediately).
Current default −0.25% (E&W).
Fixed recoverable costs tables (CPR Part 45)
Fixed publicationSource: CPR Part 45 and Practice Direction 45
Used by: Fast Track (New) · Intermediate Track · Stage 3 RTA · FT RTA (Legacy) · FT EL (Legacy) · FT PL (Legacy)
How this dataset is maintained
Statutory: changes only when legislation, an SI or a rule amendment takes effect.
Update trigger: CPR amendment (rule committee updates, typically April/October) — update the affected regime's tables.
Part 36 consequences framework
Fixed publicationSource: CPR Part 36 (r.36.17 enhancements)
Used by: Part 36
How this dataset is maintained
Statutory: changes only when legislation, an SI or a rule amendment takes effect.
Update trigger: CPR Part 36 amendment — update the consequence logic.
ET limitation & early-conciliation rules
Fixed publicationSource: ERA 1996 / EqA 2010 s.140B / ETA 1996 s.207B (stop-the-clock)
Used by: ET Date Calculator
How this dataset is maintained
Statutory: changes only when legislation, an SI or a rule amendment takes effect.
Update trigger: Statutory amendment to limitation or EC rules — update the date logic.
Forward s.207B(4) logic verified by David in the 3 Jun 2026 sweep.
State pension age rules
Fixed publicationSource: Pensions Acts 1995–2014 (SPA timetables)
Used by: State Pension Age
How this dataset is maintained
Statutory: changes only when legislation, an SI or a rule amendment takes effect.
Update trigger: A new Pensions Act changing the SPA timetable — update the rules.
Spotted something out of date, or a source you think we should be using? Please let us know.