Self Assessment is how the self-employed report income and pay tax. This guide covers who needs to file, the deadlines, payments on account, and how to avoid a nasty surprise in January.
Published July 2026 · Updated July 2026
You generally need to file if you were self-employed and earned more than £1,000, rented out property, or had other untaxed income such as dividends above the allowance. Employees taxed through PAYE often do not, unless they have extra income.
The tax year ends 5 April. For that year, the online return and any tax owed are due by the following 31 January. Register by 5 October if it is your first year. Paper returns are due earlier, by 31 October.
If your bill is over £1,000, HMRC usually asks for payments on account, two advance instalments (31 January and 31 July) towards next year's tax. In your first year this can make the January bill feel unexpectedly large.
A simple habit, moving a percentage of each payment into a separate pot, means the tax bill is already covered when it lands. Good records make the return itself quick.
It depends on your profit, allowances and other income. Setting aside a portion of income as you earn it is the safest way to be ready.
Records of all income and allowable expenses. Digital records are becoming mandatory under Making Tax Digital for Income Tax.
Contact HMRC, you may be able to set up a payment plan. Ignoring it leads to penalties and interest.
This guide is general information for UK small business owners, not accounting, tax or legal advice. Rules, rates and thresholds reflect 2026/27 and change over time; always check the linked official source or a qualified adviser for your situation.