UK calculator data sources and methodology

Which data is included?

Tax and allowance calculators use a versioned 2026/27 snapshot checked on 16 October 2026. Property tax uses the rates in force on that date. Each tool links to the relevant authority and explains its assumptions.

Income Tax offers England, Scotland, Wales and Northern Ireland. Property tax changes between SDLT, LBTT and LTT. Country is selected manually; there are no location or postcode API calls.

What needs your own figures?

Mortgage offers, savings returns and household spending use your figures and illustrative examples. Fuel tools include DESNZ UK averages dated 12 October 2026. Electricity tools include the Ofgem GB average Direct Debit cap unit rate for October–December 2026; this does not cover Northern Ireland or public EV charging. All presets are editable, dated references rather than live quotes.

How current are the rules?

This is a checked snapshot, not an automatic government feed. The rule version is uk-2026-27-2026-10-16. Announcements taking effect after this snapshot are not included. Verify the linked source before relying on a result. Calculations are estimates and do not replace official eligibility or filing calculations.

Official sources

• HMRC — Income Tax rates and allowances
• HMRC — Scottish Income Tax
• HMRC — 2026/27 employer rates and thresholds
• HMRC — Self-employed National Insurance
• HMRC — Dividend tax
• HMRC — Capital Gains Tax rates
• HMRC — Capital Gains Tax allowances
• HMRC — Tax-free savings interest
• HMRC — Pension tax relief
• HMRC — Pension annual allowance
• HMRC — Tapered annual allowance
• HMRC — Salary sacrifice
• HMRC — Child Benefit rates
• HMRC — High Income Child Benefit Charge
• HMRC — Marriage Allowance
• HMRC — Residential SDLT
• Revenue Scotland — Residential LBTT
• Revenue Scotland — Additional Dwelling Supplement
• Welsh Revenue Authority — LTT rates
• HMRC — Lifetime ISA
• HMRC — ISA allowances
• HMRC — Inheritance Tax
• HMRC — Tax-Free Childcare
• HMRC — Gift Aid
• GOV.UK — Holiday entitlement
• DESNZ — Weekly UK road fuel prices
• Ofgem — October to December 2026 cap rates
• HMRC — VAT rates
• GOV.UK — Council Tax liability and discounts
• Edinburgh Council — Single occupancy discount
• HMRC — 2026 Corporation Tax rates
• HMRC — Corporation Tax marginal relief
• HMRC — Trading and property allowances
• HMRC — Rent a Room Scheme
• GOV.UK — Statutory Maternity Pay
• nidirect — SMP calculation
• GOV.UK — Statutory Paternity Pay
• nidirect — Statutory Paternity Pay
• HMRC — Lump sum allowance
• HMRC — Employment Allowance
• HMRC — Apprenticeship Levy
• HMRC — VAT registration rules
• GOV.UK — Gas meter readings and bill calculation
• GOV.UK — Statutory redundancy pay
• nidirect — Redundancy pay and worked examples
• Department for the Economy — NI limits from 6 April 2026
• GOV.UK — Statutory Sick Pay amounts
• HMRC — Work out Statutory Sick Pay manually
• nidirect — Statutory Sick Pay
• HMRC — Self Assessment payments on account
• HMRC — Calculate the benefit of a company car
• HMRC — Company car benefit percentages, including 2026/27
• GOV.UK — Tax on company cars
• GOV.UK — Funded childcare for working parents in England
• mygov.scot — Funded early learning and childcare
• Welsh Government — Childcare Offer for Wales
• nidirect — Funded pre-school education places

Privacy

Calculator inputs are processed in your browser. CalcBrit does not send them to a calculator API or save them in an account. External source links open the authority’s own website.

Contains public sector information licensed under the Open Government Licence v3.0, except where otherwise stated. CalcBrit is independent and is not endorsed by the listed authorities.