Every calculation, openly documented.
This page documents every assumption and rate used by our calculators for the 2026/27 tax year (rules in force from 6 April 2026). Calculations are deterministic and the engine source is structured so each rate change is a single-file update.
Verified
§ 01
Income tax — England, Wales & Northern Ireland
- Personal Allowance: £12,570 (frozen until 2030/31)
- PA taper: reduces £1 for every £2 above £100,000 adjusted net income; reaches zero at £125,140
- Basic rate 20% on taxable income up to £37,700
- Higher rate 40% on taxable income £37,701 — £112,570
- Additional rate 45% above £112,570 taxable
§ 02
National Insurance
- Employee Class 1: 8% on earnings £12,571 — £50,270; 2% above
- Employer Class 1: 15% above £5,000 secondary threshold
- Apprenticeship Levy: 0.5% on full pay (umbrella scenarios)
§ 03
Corporation Tax — unchanged from April 2023
- Small profits rate 19% on profits ≤ £50,000
- Main rate 25% on profits ≥ £250,000
- Marginal Relief between (effective ~26.5% on the marginal £)
§ 04
Dividend Tax — post April 2026 rise
- Allowance: £500 (uses band space but is tax-free)
- Basic rate: 10.75% (was 8.75% in 2025/26)
- Higher rate: 35.75% (was 33.75%)
- Additional rate: 39.35% (unchanged)
For specific HMRC source links, see our sources page. For plain-English definitions of the terms used above (IR35, marginal relief, personal allowance taper, dividend allowance, JSL, etc.), see the glossary. This is informational content, not regulated financial advice. For your own situation, consult a qualified accountant.