HMRC UTR Number: What It Is and Why You Need It Before the January Deadline
If you complete a Self Assessment tax return, one reference number underpins the entire process. Your HMRC UTR number is essential for filing online, speaking to HMRC and ensuring your tax record is correctly matched to you.
As we approach the 31 January 2026 deadline for online Self Assessment returns, many people contact us because they cannot find their UTR or are unsure whether they even have one. This can delay filing and increase stress at an already busy time.
What is a UTR number?
A UTR, or Unique Taxpayer Reference, is a ten-digit number issued by HMRC. It identifies you or your business within the UK tax system. Once issued, it stays with you for life, even if your circumstances change.
You need a UTR if you are:
- Self-employed or a sole trader
- A company director completing Self Assessment
- A landlord with rental income
- Required to submit a tax return for any other reason
Without a UTR, you cannot file an online Self Assessment return.
Where to find your UTR
Your UTR is usually found on official HMRC documents, including:
- Your Self Assessment welcome letter
- Previous tax returns or payment reminders
- Your HMRC online account
If you have registered for Self Assessment but cannot locate your number, it is still recoverable. The key is acting early, as replacement letters and security checks take time.
What if you do not have a UTR yet?
If you have recently become self-employed or have new untaxed income, you may need to register for Self Assessment before a UTR is issued. This process can take several days, sometimes longer during January, which is why early actionmatters.
Leaving this too late can restrict your ability to submit your return before the deadline, even if your figures are ready.
Still can’t find it?
If you cannot access your online account and have no paperwork, call the HMRC Self Assessment helpline at 0300 200 3310. They cannot give the number over the phone for security reasons but will post it to your home address.