How to register for Self-Assessment and get your UTR

Who needs to register for Self-Assessment?

You need to register for Self-Assessment if you have income that isn't taxed automatically through Pay As You Earn (PAYE). This applies to a wide range of individuals and businesses in the UK.

You must register if any of the following applied in the last tax year (6 April to 5 April):

• You were self-employed as a sole trader and earned more than £1,000 (before taking off any expenses).
• You were a partner in a business partnership.
• You receive income from renting out a property in the UK or abroad.
• You are a company director (unless your tax is fully paid through PAYE).
• Your total income was over £100,000.
• You had to pay Capital Gains Tax.
• You had taxable foreign income.
• You need to pay the High Income Child Benefit Charge and haven't paid it through PAYE.
• You receive yearly income from a trust or settlement.
• You receive other untaxed income that cannot be collected through your PAYE tax code, such as tips or commission.

How to register for Self-Assessment

The process for registering depends on whether you are self-employed or not. In most cases, you will register online through the HMRC website.

If you are self-employed (sole trader)

1. Set up a Government Gateway account: If you don't already have one, you'll need to create a Government Gateway user ID and password. This is your access point for HMRC's online services.
2. Register as self-employed: Use the online CWF1 form. You'll need to provide details such as your National Insurance number, full name, date of birth, current address, contact details, the date you started self-employment, and your business name.
3. Submit your registration: Once completed, submit the form.

If you are not self-employed (e.g., landlord, untaxed income)

1. Set up a Government Gateway account: As above, create or use your existing Government Gateway user ID and password.
2. Register for Self-Assessment: Use the online SA1 form. You'll need to provide your National Insurance number, full name, date of birth, address, contact details, and explain why you need to register (e.g., rental income, foreign income).
3. Submit your registration: Complete and submit the form online. You can also fill in, print, and post the SA1 form if you cannot use the online service.

If you were previously registered for Self-Assessment but didn't need to send a tax return for the last tax year, you may need to reactivate your account rather than register anew. Check the HMRC website for guidance on this.

Getting your Unique Taxpayer Reference (UTR)

Your Unique Taxpayer Reference (UTR) is a 10-digit number that HMRC uses to identify you for tax purposes. It's sometimes just called your 'tax reference'.

Once you have successfully registered for Self-Assessment, HMRC will send your UTR to you by post. This typically takes around 10 working days if you are in the UK, or longer if you live overseas.

Keep your UTR safe as you will need it to file your annual tax return and for any correspondence with HMRC. You can also find your UTR in your Personal Tax Account, the HMRC app, or on previous tax returns and other documents from HMRC.

Deadlines and what happens next

The tax year runs from 6 April to 5 April the following year. For the current tax year 2026/27, this means 6 April 2026 to 5 April 2027.

Key deadlines for Self-Assessment are:

• 5 October: This is the deadline to register for Self-Assessment after the end of the tax year in which you first needed to file. For example, if you needed to file for the 2025/26 tax year (which ended 5 April 2026), you must register by 5 October 2026. If you needed to file for the current 2026/27 tax year, you must register by 5 October 2027.
• 31 October: Deadline for paper tax returns for the previous tax year. For the 2025/26 tax year, this is 31 October 2026.
• 31 January: Deadline for online tax returns and payment of any tax owed for the previous tax year. For the 2025/26 tax year, this is 31 January 2027. This is also the deadline for your first payment on account for the current tax year (2026/27), if applicable.
• 31 July: Deadline for your second payment on account for the current tax year (2026/27), if applicable.

After registering, you can submit your tax return any time after 5 April following the end of the tax year. Filing early means you'll know what you owe sooner, allowing you to budget for your tax bill.

Common mistakes

• Missing the registration deadline: Failing to register by 5 October after the end of the relevant tax year can lead to penalties, even if you file your return on time.
• Not registering when required: Many people assume PAYE income covers everything, but additional untaxed income often requires Self-Assessment.
• Incorrectly registering: Using the wrong form (e.g., CWF1 instead of SA1) or providing incomplete details can cause delays.
• Delaying registration: Waiting until the last minute to register can mean you don't receive your UTR in time to file your return by the deadline, potentially incurring penalties.