Self Employed Tax Calculator UK: how much tax will you pay?

A sole trader pays Income Tax and Class 4 National Insurance on their profit through Self Assessment, and a student loan repayment if they have one. For the 2026 to 2027 tax year (6 April to 5 April) this calculator follows the GOV.UK rules and rounds profit down to whole pounds, as HMRC's own Self Assessment calculator does.

Profit is your turnover minus your allowed business expenses, or minus the £1,000 trading allowance if that is better for you.

• Income Tax: the first £12,570 is your tax-free Personal Allowance (it falls by £1 for every £2 of income over £100,000). In England, Wales and Northern Ireland the rest is taxed at 20% up to £50,270, 40% up to £125,140 and 45% above. Scotland has six bands
• Class 4 National Insurance: 6% on profits from £12,570 to £50,270, and 2% on profits above that
• Class 2: £3.65 a week. It is voluntary below £7,105 of profit and treated as paid at or above it, so it adds nothing to the bill
• Student loan: a share of your income over the plan threshold, worked out on your whole income for the year, less anything an employer has already taken
• Payments on account: after the bill, two payments towards next year, each 50% of the Income Tax and Class 4 (not when that is under £1,000)

If you have turnover and expenses, you can claim your expenses or the £1,000 trading allowance, but not both (GOV.UK). The allowance takes off up to £1,000, and never more than your turnover.

So the allowance is better when your expenses are under £1,000, and claiming expenses is better when they are higher. Choose "Whichever is better for me" and the calculator picks the one that gives the lower profit. The allowance is not available for income from a partnership, or from a company you or someone connected to you controls.

Payments on account are payments towards your next tax bill, Class 4 included. There are two a year, due by midnight on 31 January and 31 July, and each is half of last year's tax (GOV.UK).

You do not need to make them if last year's bill was under £1,000, or if you paid more than 80% of last year's tax outside Self Assessment (for example through your tax code). Anything left after the payments on account is the balancing payment, due by 31 January the following year.

The figure we show assumes next year's profit is the same as this year's. HMRC can reduce the payments if you expect a lower profit.

Class 2 is £3.65 a week for 2026 to 2027. If your profit is £7,105 or more, it is treated as paid to protect your National Insurance record, so you pay nothing. Below that you can choose to pay voluntary Class 2 (GOV.UK). The calculator says which applies to you but adds nothing for it.

Other income uses up your tax bands, so your profit may be taxed at a higher rate. Tax on pay or a pension is normally taken by your employer or pension provider, so under More options we show the extra tax your profit causes: the tax on all your income, minus the tax on the other income alone.

Class 4 is worked out on your profit only. For a student loan, HMRC looks at your whole income for the year and takes off what your employer has already deducted (GOV.UK).

It is an estimate for sole traders, not a tax return. It does not work out:

• pension contributions and their tax relief
• the High Income Child Benefit Charge
• income from savings, dividends or property
• partnership profits, trading losses or relief for them
• the first and last years of a business, when special rules can apply
• Class 4 for people over State Pension age (we have not confirmed the rule)
• Making Tax Digital: it changes how you report, not how the tax is worked out

We ran 32 profits through HMRC's own Self Assessment tax calculator (England, Wales and Northern Ireland, and Scotland, up to £100,000 of profit) and our Income Tax, Class 4 and total match it to the penny. HMRC's tool shows the 2025 to 2026 tax year and assumes the standard Personal Allowance. The 2026 to 2027 Class 4 and Income Tax figures on GOV.UK are the same, so the arithmetic is tested at the same rates. We re-run the check each April.