Self-employed tax calculator

Your total self-employed tax bill

Unlike employed workers, self-employed people receive income gross — no tax is deducted at source. HMRC collects income tax and Class 4 National Insurance through Self Assessment, usually as a single January payment. This calculator shows the size of that bill in advance so you can plan.

Enter taxable profit after allowable business expenses — not total turnover. Expenses reduce the figure that HMRC taxes, so the gap between turnover and profit is where the planning starts.

• Tax is on profit, not turnover. Always deduct allowable business expenses first.
• The monthly set-aside figure is your number to hold in a separate account until Self Assessment.
• Add student loan or pension to see how they affect your overall net income.

Rates checked against Budget 2026 Annex A on 30 October 2026. Written and reviewed by James Whitfield against current GOV.UK and HMRC guidance. Estimates for planning only — not tax, accounting or financial advice.

What goes into a self-employed tax bill

Self-employed income is the profit you make from working for yourself, as a sole trader, a freelancer, a subcontractor or a partner in a partnership. At the personal level it is taxed the same way: your profit for the tax year is added to any other income, the Personal Allowance and Income Tax bands are applied to the total, and Class 4 National Insurance is charged on the self-employed profit alone.

If you have more than one self-employed business, the profits are added together. Each one does not get its own allowance. Three things most often change the bill from a simple estimate: tax already taken off under the Construction Industry Scheme, Scottish Income Tax rates, and other income such as a job or pension.

Three self-employed situations, worked through for 2026/27

A CIS subcontractor who is owed a refund

A registered subcontractor invoices £40,000 of labour, and contractors deduct 20% CIS, £8,000 in total. After £6,000 of expenses the profit is £34,000, so the bill is £4,286 Income Tax plus £1,285.80 Class 4 NI, £5,571.80 in all. The CIS deductions are credited against it, so HMRC owes £2,428.20 back. CIS is taken from labour only, not materials, and is 30% if you are not registered.

The same profit in Scotland and England

On £45,000 of profit, Income Tax is £6,486 in England, Wales or Northern Ireland and £6,882.05 in Scotland, where there are more bands. Class 4 NI is £1,945.80 in both, because National Insurance is UK-wide. Choose Scotland in the calculator if your main home is there.

Two small businesses

Weekday work makes £24,000 profit and a weekend business £6,000. On its own the £6,000 would sit under the £12,570 allowance, but the profits are added together: on £30,000 the bill is £4,531.80, of which £1,560.00 comes from the weekend business, taxed at 20% Income Tax plus 6% Class 4.

Every figure here comes from the calculator above, using 2026/27 rates. Estimates for planning only, not tax advice.

Common mistakes

• Throwing away CIS statements. Your contractors' monthly statements are the evidence for the deductions credited on your return.
• Expecting a Class 2 bill. Compulsory Class 2 NI ended on 6 April 2024. With profits of £7,105 or more you are treated as having paid it for State Pension purposes; below that you can pay it voluntarily, at £3.65 a week in 2026/27.
• Entering turnover instead of profit. Allowable expenses come off first; the calculator expects the figure after them.
• Forgetting the first-year jump. Once the bill is £1,000 or more, payments on account can make the first 31 January up to 150% of a year's tax.

Self-employed tax — common questions