Self Employed Tax Calculator

Self-employed tax starts with profit: annual income minus allowable expenses. The calculator adds any other PAYE income to work out how much of the personal allowance and tax bands may already be used, then estimates income tax attributable to the self-employed profit.

For 2026/27, the calculator uses the standard personal allowance and income tax bands, Class 2 National Insurance at GBP3.65 a week where applicable, and Class 4 National Insurance at 6% on profits from GBP12,570 to GBP50,270 and 2% above GBP50,270. Payments on account are shown as a simple half-and-half estimate of the bill, matching the usual 31 January and 31 July pattern.

Use the result as a practical planning estimate for income, allowable expenses, paye income, class 2 ni, class 4 ni, payments on account. The calculator is designed to make the main moving parts visible immediately, so it is most useful when you want to compare scenarios, sense-check a decision, or understand why one input changes the final result.

Before relying on the number, check whether your situation includes anything outside the calculator scope. Common examples are local rules, provider fees, payroll timing, special reliefs, bank holidays, tariff changes, exchange-rate markups, unusual tax codes, or personal circumstances that need official guidance or professional advice.

To make the estimate more accurate, use figures from the most recent bill, payslip, lender quote, receipt, official notice or provider screen you have. Rounded inputs are fine for quick comparisons, but precise inputs are better when you are deciding whether something is affordable or comparing two similar options.

Re-run the calculator whenever a key assumption changes, such as a new rate, different term, changed salary, updated threshold, extra fee, altered usage pattern or different date range. Keeping those assumptions fresh is often more useful than trying to make one calculation perfect.

If you are using the result for a formal decision, keep a note of the inputs you used and the date of the calculation. That makes it easier to compare the estimate with a later quote, bill, payslip or official calculation.