Estimate UK self-employed Income Tax and Class 4 National Insurance from trading profit, with Self Assessment caveats.
Use this self-employed tax calculator to estimate Income Tax, Class 4 National Insurance and after-tax trading profit for the 2026/27 tax year. It is a planning estimate only and does not decide Self Assessment filing duties, expenses, VAT or accounting treatment.
Enter a trading profit to see both payment dates and what falls due on each of them.
Where payments on account are due, a first year's Self Assessment bill is larger than the year's tax. Income Tax and Class 4 come to £13,888.60 for the year, and on 31 January 2028 you settle that and pay £6,944.30 towards the next year at the same time, so £20,832.90 leaves the account on one day. The second instalment of £6,944.30 follows on 31 July 2028. After that first year, and while profit stays where it is, £6,944.30 falls due each January and July with nothing left to settle between them. Payments on account are set from the year just gone rather than the year ahead, so if profit drops you can apply to reduce them — and if you do that and profit does not drop, HMRC charges interest on the difference. Class 2 National Insurance is treated as paid at this level of profit, so there is nothing to add for it and nothing to lose from the State Pension record. The figures are for the 2026/27 tax year and assume trading profit after allowable expenses is the only income, England, Wales or Northern Ireland rates, and no student loan. A student loan repayment, if you have one, is due on the January date but is excluded from payments on account. Scotland sets its own Income Tax bands, so the Income Tax inside these totals would be a different figure there.
These helpers are planning estimates only and cannot decide tax filing duties, accounting treatment, company law, dividend legality or the best salary/dividend mix.
| Personal Allowance used | £12,570 |
|---|---|
| Taxable profit | £47,430.00 |
| Class 2 status | treated as paid |
| Total tax and NI estimate | £13,888.60 |
| Tax/source year | 2026/27 |
|---|---|
| Region | England/Wales/Northern Ireland |
| Tax code basis | 1257L where the page uses PAYE defaults |
| Pension basis | No pension deduction unless this example says otherwise |
| Student loan basis | No student loan unless selected in this example |
| What is not decided here | PayBreakdown does not decide payroll correctness, lender approval, benefit entitlement or employer compliance, and does not give regulated financial, mortgage, debt, tax, payroll or legal advice. |
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The calculator models trading profit after allowable expenses, then estimates tapered Personal Allowance, Income Tax and Class 4 National Insurance from the shared source data.
Use the after-tax profit estimate for budget planning, then check official Self Assessment guidance or an accountant before making filing or business decisions.
Change any figure above and the result moves with it. A payslip can differ from any calculator because payroll works pay period by pay period, so a tax-code change, a bonus, arrears or a refund can land in one month and not the next. See how each deduction is worked out.
It estimates Income Tax, Class 4 National Insurance, taxable profit and after-tax trading profit from a self-employed profit input for the selected tax year.
No. It estimates both payment dates and what falls due on each, including the first payment on account, but it does not model losses, VAT, CIS, capital allowances, basis-period edge cases, Making Tax Digital or every expense and allowance.
No. It is a planning estimate only. Self Assessment registration, filing duties and deadlines should be checked with GOV.UK or a professional adviser.
No. Sole trader and self-employed describe the same thing for tax: an unincorporated business taxed on its profit through Self Assessment, so one calculator covers both. A limited company is a different case, because the company pays Corporation Tax on its profit and the director is taxed separately on salary and dividends.
Last updated 2026-08-27. Checked by Sean Elsmore. Rates last checked against GOV.UK on 2026-08-07. Estimates are for planning and should be checked against official records where the decision matters.