How to Register for Self-Assessment with HMRC
If you have income that has not been taxed through PAYE, you may need to register for Self-Assessment with HMRC and file an annual tax return. The registration process is straightforward but must be completed by a specific deadline to avoid penalties.
Who Needs to Register?
HMRC requires you to register for Self-Assessment if, in the previous tax year, you were self-employed as a sole trader and earned more than £1,000; you were a partner in a business partnership; you received rental income; you had untaxed income over £2,500 (such as tips or commission); you earned over £100,000; you received income from abroad; or you have complex tax affairs including trust income or capital gains above the Annual Exempt Amount. You may also need to register if you claimed Child Benefit and your or your partner's income exceeded £60,000.
The Registration Deadline
You must register by 5 October following the end of the tax year for which you need to file. The UK tax year runs from 6 April to 5 April. So if you became self-employed on 1 November 2024 (during the 2024/25 tax year ending 5 April 2025), you must register by 5 October 2025. Missing this deadline may result in a penalty, even if you ultimately owe no tax.
How to Register Online
Go to gov.uk/register-for-self-assessment and select the option that applies to you: self-employed, not self-employed, or registering a partner or partnership. You will need to create a Government Gateway account if you do not have one, using your passport or driving licence to verify your identity. You will then complete an online form with your personal details, National Insurance number, contact information, and the reason you need to file.
What Happens After Registration
HMRC will process your registration and send you a letter with your Unique Taxpayer Reference (UTR) — a 10-digit number you will use for all future communication with HMRC about your Self-Assessment. This typically arrives within 10 working days. You will then need to activate your Self-Assessment in your Government Gateway account using the activation code that arrives by post.
Registering for Class 2 NI (Historical)
Prior to April 2024, registering as self-employed also meant registering for Class 2 National Insurance. From April 2024, Class 2 was abolished and State Pension entitlement for the self-employed is now built through Class 4 NI, collected via Self-Assessment. No separate NI registration is required.
If You Were Previously Registered
If you were previously registered for Self-Assessment but deregistered (for example, because you stopped being self-employed), you can re-register through the same online process. Your original UTR will be reinstated.
First Tax Return
Your first Self-Assessment return covers the tax year in which you registered. The online filing deadline is 31 January following the tax year end. For example, if you registered for 2024/25, your first return is due by 31 January 2026. Make sure to keep records from the start of your trading so you have everything you need when the time comes.
