Self-Employed Tax Calculator 2026/27

What are current Class 4 and Class 2 rules?

For 2026/27, Class 4 is 6% on profits above £12,570 up to £50,270 and 2% above £50,270. Class 2 is no longer normally a compulsory payment: at profits of £7,105 or more it is treated as paid, while below that threshold eligible people can pay voluntarily at £3.65 a week. Historical tax years have different rules.

What should I check before relying on an estimate?

Enter taxable trading profit after allowable expenses or the applicable trading allowance, not turnover; the engine does not subtract another trading allowance. Income Tax uses England, Wales and Northern Ireland bands, not Scottish bands. Historical Class 2 and Class 4 rules are year-specific; no compulsory or voluntary Class 2 cash charge is included from 2024/25. Payments on account, losses, mixed income, other income, voluntary NI and expense eligibility are not modelled. Pension entries default to after-tax cash deductions; relief-at-source is a separate option, with allowance and eligibility checks still required.

When is Self Assessment due?

The usual online filing and balancing-payment deadline is 31 January after the tax year ends. Payments on account may also be due on 31 January and 31 July. Use HMRC guidance to establish your filing obligation and actual payment dates.

Official sources

• GOV.UK: Self-employed National Insurance
• GOV.UK: Income Tax rates and Personal Allowances
• GOV.UK: Self Assessment deadlines