What is a UTR?
A UTR (Unique Taxpayer Reference) is a 10‑digit number HMRC uses to identify you for Self Assessment and certain other tax services.
If you are filing a tax return for the first time, you normally get a UTR after you register for Self Assessment.
When do you need to request a UTR?
You will usually need to register (and receive a UTR) if you need to complete a Self Assessment tax return, for example if you:
- Are self‑employed as a sole trader.
- Have untaxed income that needs declaring.
- Need to report certain other income or gains.
If you are not sure whether you need to file, check HMRC guidance or speak to an adviser.
Before you start: what you will need
Have these details to hand:
- National Insurance number (if you have one).
- Full name, date of birth, and current address.
- Your phone number and email address.
- The date you started self‑employment (if relevant).
Step-by-step: how to register and get a UTR
- Create (or sign in to) your Government Gateway account
- Register for Self Assessment
- Wait for HMRC to issue your UTR
- Activate Self Assessment online (if prompted)
How long does it take?
In many cases you should allow:
- Up to 10 working days for UK post once HMRC has issued the letter.
- Longer during peak filing or registration periods.
If you are close to a deadline, register as early as possible.
What to do if your UTR does not arrive
If you have registered and the UTR letter has not arrived:
- Check you used the correct address.
- Allow extra time if you recently moved.
- Sign in to your HMRC online account to see if the UTR is visible in your account.
- Contact HMRC to chase it if it has been longer than expected.
Common mistakes to avoid
- Registering under the wrong category (for example, confusing self‑employed registration with other Self Assessment routes).
- Using an old address and then missing the letter.
- Leaving registration until very close to the filing deadline.
Quick checklist
Save your UTR somewhere safe
Once you receive it, store your UTR securely. You will use it for:
- Filing returns
- Speaking with HMRC
- Authorising an accountant or agent (if you use one)
If you want, tell me whether this post is for sole traders specifically, and whether you want it written in a more formal “firm website” tone or a simpler personal tone.