Self Assessment tax calculator 2026/27
Find out what you will owe HMRC — and when. Enter your self-employed income to see your Self Assessment bill for 2026/27, your payments on account, and the dates they fall due.
2026/27 (the return due 31 January 2028). Self-employment income only.
Your Self Assessment bill
2026/27- Taxable profit
- £50,000
- Income Tax
- £7,486
- Class 4 National Insurance
- £2,246
- Student loan
- £0
Tax bill for the year
Income Tax + Class 4 NI
£9,732
When you pay it
- 31 Jan 2028 — balancing payment + 1st payment on account
- £14,598
- 31 Jul 2028 — 2nd payment on account
- £4,866
Because your bill is £1,000 or more, you also pay towards next year in two instalments of half the bill.
21 June 2026
How this was calculated
We work out the Income Tax on your taxable profit (income less expenses or the £1,000 trading allowance) using your Personal Allowance and the bands for your region, then add Class 4 National Insurance (6% from £12,570 to £50,270, 2% above). That total is your Self Assessment bill. If it is £1,000 or more we add payments on account — two instalments of half the bill, due 31 January and 31 July — towards the following year. Every rate is traced to a dated gov.uk source.
The full method and every source is on our methodology page.
Built & maintained by the Pay Packet team · methodology sourced from HMRC · last reviewed 21 June 2026. About our figures →
Your Self Assessment bill, explained
Self Assessment is how HMRC collects tax that is not taken at source. If you are self-employed, your bill for a tax year is the Income Tax on your profit plus Class 4 National Insurance. There is no longer any Class 2 to add — since April 2024 it is treated as paid above the £7,105 Small Profits Threshold.
The part that catches people out is payments on account. Once your bill reaches £1,000, HMRC assumes next year will be similar and asks you to pay it in advance — half on 31 January (alongside the balancing payment for the year just ended) and half on 31 July. In a first full year of self-employment that means your January payment is one-and-a-half times the actual bill, which is why setting money aside as you go matters.
Want the take-home view instead of the bill? See the sole trader tax calculator for the full line-by-line breakdown, or the self-employed take-home calculator for monthly figures. Have a job as well? The employed and self-employed calculator shows what is left to pay through Self Assessment on top of your PAYE.
Deadlines and the payments-on-account rules are set out on gov.uk: payments on account and Self Assessment deadlines.
Self Assessment questions
- What goes into my Self Assessment bill?
- For a sole trader, the bill is the Income Tax on your profit plus Class 4 National Insurance. Class 2 is £0 (treated as paid). A student loan, if you have one, is collected through the same return. This calculator covers self-employment income; other income such as dividends, savings interest or rent would be added to it.
- What are payments on account?
- If your bill is £1,000 or more (and less than 80% of your tax was collected at source), HMRC asks you to pay towards next year’s bill in two instalments — each half of this year’s bill — due 31 January and 31 July. So in your first year you can face one-and-a-half times the bill in January: the balancing payment plus the first payment on account.
- When are the deadlines?
- Register for Self Assessment by 5 October after the tax year you started. File online and pay the balancing payment by 31 January; the second payment on account follows on 31 July. The 2026/27 return is due by 31 January 2028.
- Why is my January payment so high the first time?
- Because it combines the balancing payment for the year just gone with the first payment on account for the year ahead. After the first year it settles down — each January and July you pay an instalment, then reconcile. Setting money aside through the year is the way to avoid a shock.
- Does this include the £100,000 Personal Allowance taper?
- Yes. Above £100,000 of profit your Personal Allowance is withdrawn by £1 for every £2, which lifts the effective rate on that band to about 60%. The calculator applies it automatically.
An estimate for the 2026/27 tax year — guidance, not personal tax advice, and not a substitute for an accountant or your Self Assessment return. It assumes self-employment profit only and a standard Personal Allowance; other income changes the bill. Always check the detail with gov.uk/HMRC.