How do I register for Self Assessment?

Register online on GOV.UK by 5 October after the end of the tax year you need to report. If you were new to Self Assessment in 2025-26, that date was 5 October 2026; register now if you missed it.

Self Assessment is how HMRC collects Income Tax from people whose tax is not all taken through their pay, including sole traders and most landlords. You register online. After it, HMRC sends you a tax reference, and you then send a return for each tax year you need to. This page follows GOV.UK as checked on 15 October 2026.

Who needs to register

The tax year runs from 6 April to 5 April. You must tell HMRC by 5 October after the end of the tax year in which you first need to report. For the 2025-26 tax year, that was 5 October 2026. If you start trading or letting during 2026-27, the deadline is 5 October 2027.

Which route to use

GOV.UK has one starting page, Check how to register for Self Assessment, which sends you down the right route.

• Sole traders register as a sole trader. You need your National Insurance number. If you are already registered for Self Assessment for another reason, such as rental income, you still register again as a sole trader, so that you are registered for Class 2 National Insurance.
• If you are not self-employed, for example if your only extra income is rent, GOV.UK has a separate guide, Register for Self Assessment if you are not self-employed, with its own start button.
• If you registered before but did not need to send a return last year, you may need to reactivate your Self Assessment account instead. The service tells you how.

What happens after you register

HMRC gives you a Unique Taxpayer Reference (UTR). It is a 10-digit number, sometimes just called your tax reference. You will usually get it by post around 15 days after you register, and it takes longer if you live overseas. Once you have it, you can also find it in the HMRC app and your personal tax account.

You then send a tax return for each tax year. For 2025-26, an online return and any tax owed are due by 31 January 2027. A paper return is due by 31 October 2026. If you file online by 30 December 2026, a balance can be collected through your tax code instead, if you have one.

What this means for you

Not sure you need to send a return at all? Our free tax return checker asks a few questions and tells you.

Registering matters for Making Tax Digital for Income Tax (MTD) too. To sign up for MTD you must be registered for Self Assessment and have sent a tax return in the last 2 years. So if your self-employment and property income before expenses was over £30,000 in 2025-26, your registration and your 2025-26 return both need to be in place before MTD starts for you on 6 April 2027. If it was over £50,000 in 2024-25, MTD should already have started for you on 6 April 2026.

A tradesperson who started in 2025-26 and is paid under the Construction Industry Scheme still registers for Self Assessment in the same way. Over-deducted CIS is claimed back through your tax return, so registering on time matters.

A landlord who lets jointly counts only their own share of the rent against these limits.

Steps to register

1. Check whether you need to send a return, using the table above or GOV.UK's checker.
2. Find your National Insurance number.
3. Go to GOV.UK's Check how to register for Self Assessment page and choose the right route: sole trader, not self-employed, or reactivate.
4. Answer the questions about yourself and your income, then submit them.
5. Wait for your UTR by post, usually around 15 days, then keep it safe.
6. Keep records of your income and expenses from the start, so the return is easy to fill in.
7. Send your 2025-26 return online by 31 January 2027, and pay what you owe by the same date.
8. If your income is over £30,000 before expenses, use the free MTD check to see when Making Tax Digital starts for you.

There are guides on starting out in the trades section, and on telling HMRC about rent in the landlord section.