If you've just started working for yourself, or you've been asked for your "UTR" and have no idea what that is, this is the short version: a UTR is the number HMRC uses to identify you for tax. You need it to file a Self Assessment return, to sign up for Making Tax Digital, and to register under the Construction Industry Scheme. Here's what it is, where to find yours, and how to get one if you've never had it.
What a UTR is
UTR stands for Unique Taxpayer Reference. It's a 10-digit number — like 1234567890 — that HMRC assigns to you (or to a company) the first time you register for Self Assessment. It never changes, and it's yours alone.
You'll sometimes see it written with a K on the end (e.g. 1234567890K). That's just the format HMRC uses when the UTR doubles as a payment reference — the actual reference is the ten digits.
What you use it for
Your UTR is how HMRC ties everything you do to your tax record. You'll need it to:
- File a Self Assessment tax return
- Sign up for Making Tax Digital for Income Tax
- Register as a subcontractor under the Construction Industry Scheme (CIS)
- Give your details to an accountant or bookkeeper so they can act for you
- Make some payments to HMRC, where the UTR is the reference
How to find your UTR
If you've registered before, you already have a UTR — you just need to locate it. The fastest places:
- The HMRC app. Free to download; your UTR is shown once you sign in.
- Your personal tax account on gov.uk (sign in with your Government Gateway ID).
- Your "Welcome to Self Assessment" letter (the SA250 HMRC sent when you first registered).
- Any HMRC Self Assessment post — a notice to file, a statement of account, or a payment reminder. Look for "UTR" or "tax reference".
- Previous tax returns you or an accountant filed.
How to get one
You don't apply for a UTR by itself — you get one automatically when you register for Self Assessment. The steps:
- Check you actually need to register (most people do once self-employment income passes £1,000 gross in a tax year).
- Register on gov.uk — you'll need details like your National Insurance number, address and the date you started.
- HMRC posts your UTR, usually about 15 days later (longer if you're overseas).
- You'll also set up a Government Gateway account to file online; keep those sign-in details safe.
There's a deadline worth knowing: you must tell HMRC you need to file by 5 October after the end of the tax year in which you started. Leave registration late and you risk a penalty — and you can't file without the UTR, so don't cut it fine.
UTR vs National Insurance number
People mix these up constantly. They're different numbers doing different jobs:
- National Insurance number — format like QQ123456C (two letters, six digits, a letter). It tracks your National Insurance and benefits record and stays with you for life.
- UTR — 10 digits. It identifies you specifically for Self Assessment and tax returns.
When you register for Self Assessment you'll typically be asked for your National Insurance number, and HMRC issues your UTR as a result.
Lost or never received it
If you can't find your UTR anywhere:
- Check the HMRC app and your personal tax account first — it's almost always there.
- If you registered recently, allow the full ~15 days for the letter (longer from abroad) before chasing.
- Still nothing? Contact HMRC's Self Assessment helpline — they can confirm your UTR once they've verified your identity. HMRC won't show a full UTR over email for security reasons.