TaxWiz Logo
Updated for 2026/27
Fact Checked

What is a UTR Number? Your 10-Digit ID for HMRC Self Assessment

Everything you need to know about the Unique Taxpayer Reference (UTR) number in the UK. Learn what it is, where to find it, and why you need it for your tax return.

T

TaxWiz Editorial

Tax Content Writer • Modified 2026-04-07

The Simple Definition

Your Unique Taxpayer Reference (UTR) is a 10-digit number that HMRC uses to identify you and your business in their system.

Think of it like your "Tax DNA." Every time you call HMRC, log into your tax account, or pay your bill, you will need this number so they know exactly which "pot" of tax to apply the information to.

The Short Answer

Your UTR is a 10-digit code that belongs to you for life.

It's not sensitive in the same way a password is, but you should keep it safe. You can't even start a tax return without it.

Where to Find Your UTR

If you have already registered for Self Assessment, your UTR is hidden in plain sight on several different documents.

Check these places first:

  • The HMRC Welcome Letter: (Form SA250) sent to you when you first registered.
  • Your Personal Tax Account: On the HMRC website or the HMRC App.
  • Previous Tax Returns: Look at the top-right corner of any old filing.
  • Payment Reminders: Any letter from HMRC asking you to pay tax.

The format: It is always 10 digits long (e.g., 12345 67890). Sometimes it has a stray letter at the end or start on certain forms, but the core 10 digits are what matters.

What if I Lost My UTR?

If you are a new freelancer or you're filing for the first time in years and can't find your UTR, don't panic. You have three ways to recover it.

Action Plan: Recovering Your UTR

  1. Check your HMRC App: (The fastest way). If you have biometric login (FaceID), your UTR is visible on the home screen.
  2. Search your emails: Look for "HMRC" or "Government Gateway."
  3. Call the Self Assessment Helpline: (The slowest way). Be prepared for a 45-minute wait time, especially in January.
Go to HMRC Portal

Is it a Private Number?

Unlike your passwords, your UTR is not a "secret" code, but you should be careful who you share it with.

Important Security Rules
  • Never give your UTR to someone claiming to be from HMRC over the phone (HMRC already knows your number).
  • Only share your UTR with your registered accountant or a trusted tax software provider (like Xero or FreeAgent).
  • Be wary of 'Tax Refund' scams asking for your UTR and bank details via text message.

Your Next Step

If you have your UTR and you are ready to file, your next job is to work out what you owe and what you can claim.

Ready to Move Forward?

  1. If you DON'T have a UTR yet, follow our How to Register guide.
  2. If you DO have it, start recording your Allowable Expenses.
  3. Not sure if you need to file? Take the Do I Need to Register? test.
Return to Hub

Frequently Asked Questions

No. Your NI number is for your pension and benefits. Your UTR is strictly for telling HMRC about your tax returns. You will have both.
No. Once HMRC issues you a UTR, it is yours for life, even if you stop being self-employed and then start again years later.
No. You only get a UTR once you have officially notified HMRC that you have a reason to file a tax return (e.g. you've started a side hustle over £1,000).

Tax Disclaimer: TaxWiz provides general educational information and guides for UK residents. While we strive to maintain accuracy for the 2026/27 tax year, tax rules are subject to change. This content does not constitute regulated financial, legal, or tax advice. For complex situations, we strongly recommend consulting a qualified UK accountant. View our full Disclaimer.