How do you file Self Assessment taxes in the United Kingdom in 2026?

You must send a return if HMRC asks you to. You also must file when, in the last tax year (6 April to 5 April), you were a sole trader earning more than £1,000 before allowable reliefs, a partner in a business partnership, owed Capital Gains Tax on a disposal, owed the High Income Child Benefit Charge outside PAYE, or were an off-payroll worker repaying a student or postgraduate loan through Self Assessment rules.

Untaxed income can also trigger a return: UK property rent, tips, savings interest, dividends, foreign income, or taxable UK income while you are non-resident. Use the official GOV.UK checker if you are unsure. A pure PAYE employee with only taxed wages often never files Self Assessment, even after moving to London or Manchester.

If you need a return for the previous year and have never filed (or registered before but did not need a return for that year), tell HMRC by 5 October after the tax year ends. Registration issues your Unique Taxpayer Reference (UTR), the personal Self Assessment ID you need to submit.

Start the return any time after 5 April for the year just ended. Online filing runs until 11:59pm on 31 January. Paper SA100 returns must reach HMRC by 31 October. If you want a small Self Assessment bill collected through your PAYE tax code, file online by 30 December so HMRC can try that collection route when the other conditions are met.

Keep bank statements, invoices, property records, and foreign income evidence ready. Scottish taxpayers can face different Income Tax bands from England and Northern Ireland, and Welsh rates can also diverge, so the address and residence status held by HMRC matter when the calculation runs. Match your National Insurance number on the return to payroll and identity records: get a National Insurance number.

Pay any bill by the 31 January deadline. Late filing triggers an automatic £100 penalty even when no tax is due, with further penalties as the return stays outstanding. Use a UK current account you already control for payments after you open a UK bank account.

If you no longer need Self Assessment, tell HMRC formally. Until HMRC confirms you can stop, keep filing when a notice to file arrives. Sequence this with other arrival tasks in paperwork after moving to the UK.