When do I need to register for Self Assessment?

Do you need to file a Self Assessment tax return?

Self Assessment is how HMRC collects tax on income that is not taxed at source. You must send a tax return if, in the tax year (6 April to 5 April), any of these applied:

• you were self-employed as a sole trader and earned more than £1,000 (before taking off anything you can claim)
• you were a partner in a business partnership
• you have to pay Capital Gains Tax on something you sold
• you have to pay the High Income Child Benefit Charge and it is not collected through PAYE
• you got dividends over £10,000

You may also need to file if you had other untaxed income, such as rent, tips, commission, savings interest, dividends or income from abroad. If HMRC writes asking you to send a return, you must send one, even if none of the above applies.

Not sure? Use HMRC's online "check if you need to send a tax return" tool first.

Key dates for the 2025/26 tax year

If you register after 5 October 2026 and do not pay your full bill by 31 January 2027, you may get a "failure to notify" penalty. It is based on the amount still unpaid.

How to register: step by step

1. Check you need to. Use the GOV.UK checker for the 2025/26 tax year.
2. Start the registration service. Go to "Register for Self Assessment" on GOV.UK and select Start now.
3. Sign in or create sign-in details. You use Government Gateway (a user ID and password) or GOV.UK One Login (an email address and password). New users are guided through creating one.
4. Answer the questions. The service asks why you need to file, for example because you are self-employed or have other income.
5. Get your UTR. HMRC gives you a Unique Taxpayer Reference (UTR), which you use for your tax returns. GOV.UK has a page on how long to wait for it.

If you registered before but did not need to send a return for 2024/25, you may need to reactivate your account instead. The service tells you how.

Timing

If you have missed the 5 October 2026 deadline, register as soon as you can anyway. The failure to notify penalty is linked to tax still unpaid after 31 January 2027, so paying your bill in full by then matters most.

After you register

• Send your return once you have your UTR.
• You can check your Self Assessment reference and what you owe in the HMRC app.
• If you miss the filing deadline, there is an automatic £100 penalty. After 3 months, £10 a day is added (up to £900). Further penalties follow at 6 and 12 months.

If you live in Scotland, Wales or Northern Ireland

Self Assessment works the same way across the UK, with the same deadlines. If you live in Scotland, Scottish Income Tax applies to your wages, pension and most other taxable income, but you pay the same tax as the rest of the UK on savings interest and dividends.

Related guides

• What is a UTR number?
• What are the Self Assessment deadlines?
• What are payments on account?
• What is the penalty for filing a Self Assessment tax return late?
• What is the trading allowance?

Where this comes from

• Register for Self Assessment (GOV.UK)
• Who must send a tax return (GOV.UK)
• How to report tax on dividends (GOV.UK)
• Self Assessment penalties (GOV.UK)
• Sign in to HMRC online services (GOV.UK)
• Download the HMRC app (GOV.UK)
• Scottish Income Tax (GOV.UK)