Skip to content
Money GuideAll guides
How-to · Step-by-step

How to file a UK Self Assessment tax return online

In short. Register for Self Assessment by 5 October after the tax year. File online by 31 January (paper by 31 October). Pay tax owed by 31 January, with payments on account by 31 July.

Self Assessment is HMRC's way of collecting Income Tax from people whose tax isn't fully collected through PAYE — including the self-employed, landlords, high earners and those with significant savings or dividend income.

Last reviewed:

·Estimated time: 3 days·Cost: Free — only tax owed is payable

What you'll need

  • UTR (Unique Taxpayer Reference) and Government Gateway login
  • Income records (invoices, P60, P45, P11D, bank interest, dividend statements)
  • Expense records (receipts, mileage logs)
  • Pension and Gift Aid contributions

The steps

  1. 01

    Register if it's your first return

    Register by 5 October after the end of the tax year you need to file for. The route differs slightly for self-employed, partners and 'not self-employed'. HMRC will post your UTR — usually within 10 working days.

    Official link →

  2. 02

    Gather your records

    Pull together income and expense records for the tax year (6 April → 5 April). Make sure to include all sources: employment, self-employment, rental, dividends, interest, foreign income.

  3. 03

    Sign in and start the return

    Log in to HMRC Online Services or the HMRC app. Add the supplementary pages that apply (SA103 self-employed, SA105 land & property, SA106 foreign etc.).

  4. 04

    Check the tax calculation

    HMRC shows the tax calculation as you complete the return. Check the Personal Allowance, basic-rate band, dividend allowance, savings nil-rate band and any pension/Gift Aid relief look right.

  5. 05

    Submit and pay

    Submit before 31 January (online). Pay any balance due plus first payment on account for the next year by 31 January; second payment on account by 31 July (if applicable).

    Official link →

Common pitfalls

  • Late filing: £100 penalty even if no tax is due; further penalties accrue after 3, 6 and 12 months
  • Late payment: interest from 1 February + 5% surcharges at 30 days, 6 months and 12 months
  • Payments on account are tax 'in advance' — they catch many first-time filers out

FAQ

Who has to file a Self Assessment return?
Self-employed earning over £1,000, partners, landlords (over £1,000 rental income), high earners (over £150,000 from 2024/25), people with untaxed income or capital gains. Use the GOV.UK checker if unsure.
What are 'payments on account'?
Two advance payments towards your next year's tax bill, each 50% of last year's liability. Due 31 January and 31 July. They don't apply if your bill is under £1,000 or 80%+ of your tax is collected at source.
Can I file on paper?
Yes, but only by 31 October — three months earlier than the online deadline. Most people file online.
← All how-to guides