Self Assessment,
explained.

Self Assessment is how HMRC collects income tax from people whose tax isn't taken automatically through payroll.

Who has to file

You usually need to file if you earned more than £1,000 from self-employment in a tax year. Landlords and people with other untaxed income may also need to.

The tax year

The UK tax year runs from 6 April to 5 April the following year.

Key dates

• Register with HMRC by 5 October after the tax year you started trading.
• File your return online and pay what you owe by 31 January.
• If your bill is over £1,000, you may also make a payment on account by 31 July.

What you pay

You pay income tax on your profit above the Personal Allowance, which is £12,570 for the 2025/26 tax year. You also pay Class 4 National Insurance on profits above a threshold.

Rates can change each year, and Scotland sets its own income tax bands. Check gov.uk for the current figures.

How to make it easier

Keep records through the year, not at the end. Track income and expenses as they happen. Set money aside for the bill as you earn.

What changes under Making Tax Digital

Since April 2026, sole traders over the first income threshold have had to keep digital records and send quarterly updates, while still submitting one tax return each year. See the guide to Making Tax Digital.

Self Assessment is simpler when the records are already done. That is the part to get right.