How to File a UK Self Assessment Tax Return
If you are self-employed, a landlord, or have untaxed income, you must register for Self AssessmentUK Self Assessment tax return — The system for reporting income that is not taxed at source — self-employment, rent, foreign income — to HMRC by 31 January each year.Click for official info ↗, get a UTRUnique Taxpayer Reference — The 10-digit number HMRC assigns for Self Assessment. You need it to file a UK tax return.Click for official info ↗, and file by 31 January after the tax year. File online, pay by the deadline, and watch out for payments on account.
The Steps
Follow these in order
Each card shows the phase, expected time, and any cost. Data checked against official UK sources(2025-Latest).
0 of 7 steps
- Before You Go 15 min
Check whether you must file
You must file if self-employed with income over £1,000, a landlord earning £1,000+ rent, a company director, or you have untaxed income over £2,500 (savings, foreign income, tips). Higher-rate earners claiming child benefit must also file. The threshold changes — check the current rules each year.
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- Before You Go 10–15 working days
Register for Self Assessment and get your UTR
First-time filers register online — self-employed register for Class 2 NICs and Self AssessmentUK Self Assessment tax return — The system for reporting income that is not taxed at source — self-employment, rent, foreign income — to HMRC by 31 January each year.Click for official info ↗ together. HMRCHM Revenue & Customs — The UK tax authority. It collects income tax, issues National Insurance numbers, and runs Self Assessment.Click for official info ↗ posts a 10-digit UTRUnique Taxpayer Reference — The 10-digit number HMRC assigns for Self Assessment. You need it to file a UK tax return.Click for official info ↗ within 10–15 working days (21 if abroad), followed by a Government Gateway activation code. Register by 5 October following the tax year you owe.
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- Fill / Prepare 2–4 hours
Gather income and expense records
For the 2024/25 tax year (6 April 2024 to 5 April 2025): employment income (P60), self-employment invoices and allowable expenses, rental income, savings interest, dividends, pension contributions, and Gift Aid. The tax-free personal allowance is £12,570 (2024/25).
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- Fill / Prepare 1–2 hours
File the return online
Sign in with your Government Gateway at tax.service.gov.uk. The online form walks through each section and calculates the tax for you. Paper returns (deadline 31 October) miss automatic calculation. Save as you go; submit before 31 January midnight.
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- Submit & Pay 15 min
Pay what you owe
Tax owed for the year is due 31 January (online filing). HMRCHM Revenue & Customs — The UK tax authority. It collects income tax, issues National Insurance numbers, and runs Self Assessment.Click for official info ↗ also collects "payments on account" — advance instalments towards next year (each 50% of your bill) due 31 January and 31 July. Pay by bank transfer, debit card, or Direct Debit; budget for the on-account amounts.
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- Follow Up Ongoing
Check your bill and keep records
Your online account shows payments, statements, and future deadlines. Keep records 5 years after the 31 January submission deadline. Late filing: £100 immediately, then escalating; late payment: interest plus 5% surcharges at 30 and 6 months.
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- Receive —
Confirmation and refunds
You get an on-screen confirmation and email receipt when filing. Overpaid tax is refunded to your bank within days (or held against future bills if you prefer). HMRCHM Revenue & Customs — The UK tax authority. It collects income tax, issues National Insurance numbers, and runs Self Assessment.Click for official info ↗ never phones threatening arrest — that is a scam.
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FAQ
Frequently Asked Questions
What happens if I miss the 31 January deadline?
An automatic £100 penalty applies even if you owe nothing, plus £10/day fines after 3 months, percentage-based penalties after 6 and 12 months, and interest on unpaid tax. If you cannot pay, contact HMRCHM Revenue & Customs — The UK tax authority. It collects income tax, issues National Insurance numbers, and runs Self Assessment.Click for official info ↗ about a Time to Pay arrangement BEFORE the deadline — they are far more flexible when you approach them first.
I only earn a little from freelancing. Do I still need to file?
Under £1,000 self-employment income: no (trading allowance). Over £1,000: yes, register and file, though the trading allowance itself means the first £1,000 is tax-free. Claiming means-tested benefits can also be a reason to file regardless of income.
What are payments on account?
If your tax bill exceeds £1,000 and under 80% of your tax comes from PAYE, HMRCHM Revenue & Customs — The UK tax authority. It collects income tax, issues National Insurance numbers, and runs Self Assessment.Click for official info ↗ collects half of the current year's expected bill in advance — on 31 January and 31 July. First-time bills are often double what people expect. You can apply to reduce payments on account if your income is falling.
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