What Is a UTR Number? How to Find Your UK Tax ID (2026)
- A UTR (Unique Taxpayer Reference) is the 10-digit number HMRC uses to identify you for Self Assessment.
- You get one automatically when you register for Self Assessment or set up a limited company.
- Find it on HMRC tax documents, in your Personal Tax Account, or the HMRC app.
- It usually arrives by post around 15 days after you register — longer if you're overseas.
- A UTR is not the same as your National Insurance number or your tax code.
- Need to register or file? Our Self Assessment service handles it for you.
If you've just gone self-employed or started a company, you'll quickly hit a form asking for your "UTR" — and if you don't know what that is, you're not alone. The UTR is your unique tax ID in the UK, and you can't file a Self Assessment return without it. This guide explains exactly what a UTR number is, how to find yours, how to get one if you don't have it, and how it differs from the other numbers HMRC uses.
What is a UTR number?
A UTR — Unique Taxpayer Reference — is a 10-digit number that HMRC uses to identify you or your business for tax purposes. It's sometimes just called a "tax reference." Every person or entity registered for Self Assessment has one, and it stays with you for life.
Think of it as your personal reference in HMRC's system: whenever you file a return, make a payment, or an accountant acts on your behalf, the UTR is how HMRC knows the tax relates to you. Without it, you simply can't submit a Self Assessment tax return.
What does a UTR number look like?
A UTR is 10 digits, for example 1234567890. You'll sometimes see it written with a letter "K" on the end — that's not part of the number itself, but the format HMRC asks for when you use your UTR as a payment reference (so your UTR plus K, giving an 11-character reference). On paper it's often labelled "UTR", "Unique Taxpayer Reference", or "tax reference".
Where can you find your UTR number?
If you've registered before, your UTR is already sitting in several places. The quickest are:
- Your Personal Tax Account on gov.uk
- The HMRC app on your phone
- Your previous Self Assessment tax returns
- Your "Welcome to Self Assessment" (SA250) letter from when you first registered
- Notices to file a return, statements, and payment reminders from HMRC
Almost any official letter HMRC has sent you about Self Assessment will have the UTR printed near the top. If you use an accountant, they'll have it on file too.
How do you get a UTR number?
You don't apply for a UTR directly — you get one automatically when you register for Self Assessment (as a sole trader, landlord, or anyone else who needs to file). Once you register, HMRC posts your UTR to you, usually around 15 days later — allow longer if you're registering from abroad.
Because of that delay, it pays to register early rather than close to a filing deadline. If you're just starting out as self-employed, our guide on how to register as a sole trader walks through the whole process, and getting your UTR is part of it.
Company UTR vs personal UTR
These are two different numbers, and mixing them up is a common mistake. Your personal UTR is for your own Self Assessment. A company UTR is issued to a limited company for Corporation Tax, separately, when the company is set up.
If you run a limited company and also file a personal return, you'll have both: a company UTR for the company's Corporation Tax and your own personal UTR for your Self Assessment. A company's Corporation Tax UTR can be requested online from HMRC, and it's sent to the company's registered office address.
What if you've lost your UTR?
Don't panic — a UTR is never cancelled, so yours still exists. First, check the places listed above: your Personal Tax Account and the HMRC app are the fastest, and any old HMRC letter will show it.
If you genuinely can't find it, contact HMRC's Self Assessment helpline and they can confirm it — for security they'll usually post it to your registered address rather than read it out over the phone. It's worth storing it somewhere safe once you have it, because you'll need it every year.
Is a UTR the same as a tax code or NI number?
No — these are three separate things, and it's the confusion that trips people up most:
| Number | Format | What it's for |
|---|---|---|
| UTR | 10 digits | Identifies you for Self Assessment |
| National Insurance number | 2 letters, 6 digits, 1 letter | Tracks your NI contributions and benefits |
| Tax code | e.g. 1257L | Tells your employer how much tax-free pay you get |
In short: your UTR is for Self Assessment, your National Insurance number is your lifelong social-security ID, and your tax code controls PAYE deductions from a salary. If a form asks for your "tax ID" in a Self Assessment context, it means your UTR.
Frequently asked questions
What is a UTR number?
A UTR (Unique Taxpayer Reference) is a 10-digit number HMRC uses to identify you or your business for Self Assessment. You get one when you register for Self Assessment or set up a limited company, and you need it to file a tax return.
How many digits is a UTR number?
A UTR is 10 digits long. When used as a payment reference to HMRC it's followed by the letter K, making an 11-character reference, but the UTR itself is the 10 digits.
Where do I find my UTR number?
In your Personal Tax Account, the HMRC app, previous tax returns, your "Welcome to Self Assessment" letter, or any HMRC notice to file, statement or payment reminder. An accountant acting for you will also have it.
How long does it take to get a UTR?
HMRC usually posts your UTR around 15 days after you register for Self Assessment, and longer if you're registering from overseas. Register early so you have it in good time before any filing deadline.
Is a UTR the same as a National Insurance number?
No. A UTR is a 10-digit Self Assessment reference; a National Insurance number is a separate lifelong ID (two letters, six digits and a letter) that tracks your NI contributions. They are used for different things.
We'll register you for Self Assessment, get your UTR sorted, and file your return for a fixed fee — no jargon, no missed deadlines. Get a quote or message us today.
Related: our Self Assessment tax return service and UK tax & accounting services. Official guidance is on the gov.uk find your UTR page.