Pillar Guide · Updated July 2026
UTR Numbers and Self-Assessment Registration: A Complete UK Guide for 2026/27
If you have just become self-employed, started freelancing, or need to declare other untaxed income, one of your first jobs is registering with HMRC for Self-Assessment and getting your Unique Taxpayer Reference. This guide explains the process, timing and what to do if things go wrong.
What a UTR Number Is
A Unique Taxpayer Reference (UTR) is a ten-digit number HMRC uses to identify you, or your company, for tax purposes, most importantly Self-Assessment. You need a UTR before you can file a Self-Assessment tax return, and it stays the same for as long as you continue to be registered.
Who Needs to Register
You typically need to register for Self-Assessment if you become self-employed or a partner in a business partnership, have significant untaxed income such as rental or investment income, or otherwise meet HMRC's criteria for needing to complete a tax return. Even relatively small amounts of self-employed or side income can trigger a registration requirement.
How to Register
Registration is done through HMRC's online service, where you provide your personal details, National Insurance number, and information about why you need to register (for example, the date you became self-employed). Once processed, HMRC posts your UTR to you, and you set up your online account access separately with an activation code.
The Registration Deadline
You generally need to register for Self-Assessment by 5 October following the end of the tax year in which your requirement to file began. For example, if you became self-employed partway through a tax year, you should register well before the following 5 October to avoid the risk of a late registration.
How Long It Takes to Get a UTR
Processing and postal times mean it can take several weeks to receive your UTR after registering, and this can be longer around busy periods such as close to filing deadlines. Register as early as possible once you know you need to, rather than waiting until close to a deadline.
Finding Your UTR
Once registered, your UTR appears in your HMRC online Self-Assessment account, on previous tax returns, and on official HMRC correspondence such as notices to file a return or payment reminders. Keep a note of it somewhere secure, since you will need it every time you deal with HMRC about your Self-Assessment affairs.
What to Do If You Lose It
If you cannot find your UTR, check previous HMRC letters, your online account, or old tax returns first. If you still cannot locate it, you can contact HMRC directly to have your UTR confirmed, though for security reasons it will usually be sent by post rather than given over the phone or by email.
Company UTRs
A limited company is issued its own separate UTR by HMRC shortly after incorporation, used for Corporation Tax purposes, which is distinct from the personal UTR of any individual director or shareholder. Directors who are also self-employed or need to file personal returns will hold a separate personal UTR as well.