How to use this UK self-employed tax calculator

A self-employed tax calculator estimates what trading profits might owe in Income Tax and Class 4 National Insurance for the 2026/27 tax year (6 April 2026 to 5 April 2027). It is a planning sketch for sole traders and freelancers — not Self Assessment software and not tax advice. You can switch England, Wales, and Northern Ireland (shared rUK bands) versus Scotland, add a student loan plan, and compare a simplified limited company (salary at the personal allowance, corporation tax, then dividends).

  1. Enter net profit. Use profit after allowable expenses, not turnover. If you have already deducted expenses, leave the £1,000 trading allowance off.
  2. Choose where you live. Non-savings, non-dividend income tax is devolved in Scotland. National Insurance is UK-wide.
  3. Add a student loan plan if you have one. Plan 1, 2, 4, 5, and postgraduate loans use different thresholds. The calculator takes a simple 9% or 6% of profit above that threshold — HMRC’s exact calculation can differ if you also have PAYE income.
  4. Keep the personal allowance on unless it is already used. The £12,570 allowance is included by default and still tapers from £100,000. Turn it off if employment or other income has already used it, so trading profits are taxed from the first pound.
  5. Read income tax, Class 4 NI, and a payment on account. Payments on account are due 31 January and 31 July; this page shows half of this year’s income tax and Class 4 as a savings target, which matches the usual 50% rule when you are in the regime.
  6. Compare the limited-company sketch. It is deliberately simple: salary at £12,570, employer NI above the secondary threshold, corporation tax with the 19%/25% structure, then dividend tax. It will not match a specialist’s extraction plan.
  7. Save the year. Optional history stores the inputs so you can compare “what if I earn £10,000 more.”

VAT, Making Tax Digital, pension contributions, the high-income child benefit charge, and Marriage Allowance are out of scope. If the number is large enough to hurt, use GOV.UK or an accountant.

Why UK self-employed tax is not a payslip calculator

Employees see PAYE and Class 1 NI withheld. Sole traders pay Income Tax and Class 4 NI through Self Assessment, usually with payments on account. A “take-home pay” tool built for PAYE understates the bill.

  • Class 4 is the line people forget. 6% between £12,570 and £50,270 and 2% above is on top of Income Tax. Class 2 is credited automatically above the small-profits threshold in 2026/27, so it is not added as a cash cost here.
  • Scotland starts higher rates sooner. The 42% Scottish higher rate begins at a lower slice of income than rUK’s 40% band. Switching the region control is the fastest way to see that.
  • The personal allowance tapers from £100,000. Losing £1 of allowance for every £2 of extra income creates a 60%-style marginal band. The calculator reduces the allowance automatically.
  • Limited company is not automatically cheaper. Employer NI and corporation tax can outweigh dividend rates at modest profits. The side-by-side “keep” figures are there so you do not incorporate on a hunch.
  • Your numbers stay local. Profit is not uploaded unless you save history.

Schedule D, Self Assessment, and the browser estimate

Self-employed taxation in Britain ran for decades through Schedule D assessments and, from 1996/97, Self Assessment. National Insurance for the self-employed split into a flat Class 2 stamp and profit-related Class 4. Class 2 was reformed so that, for most people with profits above the small-profits threshold, credits accrue without a separate weekly bill — which is why a 2026/27 sketch focuses on Class 4.

Income tax devolution gave Scotland its own bands; Wales and Northern Ireland still follow rUK rates on earned income. Corporation tax’s two-rate structure (19% small profits, 25% main rate, marginal relief between) is why a limited-company comparison cannot be “income tax minus 20%.” Desktop tax software in the 1990s let a trader change profit and watch the bill move. Web estimators followed, often as lead-gen for filing products.

Keeping 2026/27 bands, Class 4, student loans, and a compact company sketch in a dedicated JavaScript module means the rates can be updated after each Budget without an app install. It will not match your tax return. It will tell you whether you should be setting money aside before 31 January.