Self-Employed Tax Calculator 2026/27
Your Self Assessment bill — income tax plus Class 4 National Insurance — with the payments-on-account shock shown honestly: your first January payment can be 150% of your bill. Nothing you enter leaves your browser.
- Rates: GOV.UK — checked 5 Nov 2026
- Tested against HMRC worked examples
- Your salary never leaves your browser
Profit = income minus expenses. Or enter your profit directly below and leave these blank.
Optional — shares your personal allowance with your profit.
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Your Self Assessment bill — 2026/27
— / year
- Set aside
- —
- Due 31 Jan (first year)
- —
- Due 31 Jul
- —
Your profit, split — income tax, Class 4 National Insurance and what you keep.
| Profit | — |
|---|---|
| Income tax | — |
| Class 4 National Insurance | — |
| Class 2 National Insurance | — |
| Total bill | — |
| Payment on account (each) | — |
Rates checked 5 November 2026.
Every figure checked against HMRC's own examples.
Your salary never leaves your browser.
Rates re-checked by hand after every Budget.
Rates: GOV.UK — last checked 5 November 2026 See the official rates
How this is calculated
Profit is your turnover minus allowable expenses (or the profit figure you enter directly). Income tax uses the same bands and £12,570 personal allowance as employees, on your total income — profit plus any other employment income. Class 4 National Insurance is charged on your profit alone: 6% between £12,570 and £50,270, then 2% above. Class 2 is treated as paid once profit reaches the £7,105 small-profits threshold, so there is nothing to pay; below it you can pay voluntary Class 2 at £3.65 a week to protect your National Insurance record. If your bill is over £1,000, payments on account apply: two instalments of half your bill, due 31 January and 31 July — and a first-year filer pays the whole bill plus the first instalment on the first 31 January. Figures use the 2026/27 rates, last checked against GOV.UK on 5 November 2026. See the full method on How we calculate.
Worked example — £30,000 profit, first year of trading
Hand-checked against the GOV.UK Self Assessment rules (income tax bands, Class 4 rates and the payments-on-account pattern). No other income, standard personal allowance, England, Wales or Northern Ireland rates, no student loan.
| Part of the bill | Working | Amount |
|---|---|---|
| Income Tax | 20% of (£30,000 − £12,570) | £3,486.00 |
| Class 4 National Insurance | 6% of (£30,000 − £12,570) | £1,045.80 |
| Class 2 National Insurance | Profit above the £7,105 threshold — treated as paid | £0.00 |
| Bill for 2026/27 | £4,531.80 | |
| First payment on account | Half of £4,531.80 | £2,265.90 |
| Due by 31 January 2028 | Bill + first payment on account | £6,797.70 |
| Due by 31 July 2028 | Second payment on account | £2,265.90 |
Set aside 15.1% of every invoice — about £15 from every £100 you bill — and January will not hurt.
Related calculators & reading
- Self-employed? Your first tax bill — and the payments-on-account shock — the full explainer behind this tool.
- IR35 calculator — inside vs outside, if you trade through a limited company.
- Umbrella company calculator — the deduction waterfall if you work through an umbrella.
- UK tax rates 2026/27 — every band, threshold and allowance behind these figures.
Questions
How much tax will I pay as a sole trader?
Income Tax on your total income (profit plus any employment income) at the same bands as employees, plus Class 4 National Insurance on your profit alone — 6% between £12,570 and £50,270, then 2%. Class 2 is treated as paid once your profit reaches £7,105, so there is nothing extra to pay. Enter your profit above for the exact bill.
What are payments on account, and why is my first January bill so big?
If your Self Assessment bill is over £1,000, HMRC asks you to pay next year's tax in advance: two instalments of half your bill, due 31 January and 31 July. In your first year you have made no advance payments, so the first 31 January brings the whole bill plus the first instalment — 150% of your bill in one go. On a £30,000 profit that is £6,797.70, not £4,531.80.
How much should I set aside from every invoice?
The calculator shows a set-aside percentage — your bill as a share of your profit. On a £30,000 profit it is 15.1%, so about £15 from every £100 you bill. Put it in a separate account the day the invoice is paid, and January will not hurt.
What is the trading allowance?
£1,000 of gross trading income a year is tax-free. If your gross trading income is £1,000 or less you do not need to declare it at all; above £1,000 you can deduct the £1,000 allowance instead of your actual expenses (not both). It rises to £3,000 from 6 April 2027.
Is my information sent anywhere?
No. The calculator runs entirely in your browser. Nothing you enter is sent to a server, stored, or shared.
The rates behind this calculator: 2026/27 rates, sourced from GOV.UK.