Your UTR (Unique Taxpayer Reference) is a 10-digit number HMRC issues when you register for Self Assessment. If you've registered before, it's in your HMRC personal tax account, the HMRC app, or on any letter HMRC has sent you about your tax return.
What a UTR actually is
According to gov.uk's guidance on finding a lost UTR, a UTR is issued when you register for Self Assessment or set up a limited company, and it's a 10-digit number — sometimes called simply a "tax reference." It's how HMRC identifies your Self Assessment record specifically, distinct from your National Insurance number, which identifies you across the wider tax and benefits system and never changes.
You need your UTR to file a Self Assessment return, and HMRC also uses it as a reference on any correspondence about your Self Assessment account — statements, reminders, and notices to file all quote it.
Where to look if you've registered before
Gov.uk lists the same set of places for individuals and sole traders:
- Your Personal Tax Account — sign in at gov.uk/log-in-register-hmrc-online-services.
- The HMRC app — available on iOS and Android, linked to the same account.
- Previous tax returns — if you've filed before, your UTR is on the return itself.
- Other HMRC documents — specifically "notices to file" and payment reminders, both of which quote your UTR in the header or reference line.
If you're looking for a company's UTR rather than an individual's, the sources are similar in kind but come from your Corporation Tax correspondence rather than Self Assessment letters — a limited company's UTR is separate from any individual director's own Self Assessment UTR. Gov.uk notes that a company can request its Corporation Tax UTR online, and HMRC will send it to the company's registered business address held with Companies House — not to a director's personal address, and not by email, so it's worth checking that Companies House record is current if a request seems to be taking longer than expected.
This distinction trips people up specifically because a company director is often two taxpayers at once for HMRC's purposes: the company itself, which files Corporation Tax under its own UTR, and the director personally, who may separately need to file Self Assessment (for dividends, for example) under a UTR of their own. The two references are unrelated to each other and neither substitutes for the other.
UTR vs Government Gateway ID — a common mix-up
Your UTR is not the same thing as the credentials you use to sign in online, and mixing the two up is one of the most common reasons people think they've "lost" a UTR when they've actually just lost their sign-in details instead. To access HMRC's online services at all, you sign in with either a Government Gateway user ID — described on gov.uk as "a user ID (up to 12 characters) and password" — or a GOV.UK One Login, using an email address and password. Neither of those is your UTR. Your UTR is the 10-digit reference that identifies your tax record once you're signed in, not the credential that gets you signed in in the first place.
If you can't remember your Government Gateway user ID or password, that's a separate recovery process from finding a UTR — gov.uk's sign-in page has a "Create new sign in details" option that walks you through re-establishing access, after which your existing UTR and tax record are still there, unchanged, once you're back in.
If you've never registered — how you get one
A UTR isn't something you request on its own; it's generated automatically when you register for Self Assessment. Once you've registered, gov.uk says you'll "usually get your UTR by post around 15 days after you register" — longer if you live overseas. That 15-day window is why registering early matters, particularly if you're approaching the 5 October registration deadline covered in our self assessment deadline 2026/27 guide: you can't file without a UTR, and it doesn't arrive instantly.
Gov.uk also notes that if you registered for Self Assessment in the past but didn't need to file a return last year, you may need to reactivate your existing Self Assessment account rather than register — and re-registering from scratch isn't guaranteed to reissue the same UTR quickly, since the record already exists under the old reference.
If you genuinely can't find it anywhere
Work through the sources in this order before contacting HMRC, since each is faster than a phone call or letter:
- Personal Tax Account — the fastest route if you've ever signed in before. If you've forgotten your sign-in details rather than your UTR, recovering those (see above) gets you back to the same place.
- HMRC app — same login, useful if you don't have your Personal Tax Account credentials to hand on a computer, or if you're checking on the move.
- Any HMRC letter — a notice to file, a Self Assessment statement, or a payment reminder all carry it, usually printed near the top of the letter or in the reference line.
- A previous accountant or filing software — if someone else filed on your behalf, they'll have used your UTR and can usually pass it back to you; it's also worth checking any PDF copy of a previously filed return you kept for your own records.
If none of those work, gov.uk's guidance directs you to contact HMRC directly through its Self Assessment contact service, since a UTR is tied to your specific tax record and can't be reissued or looked up through a generic support channel.
A note on scams
Because a UTR is one of the pieces of information used to identify you to HMRC, it's also something phishing attempts try to extract by pretending to be HMRC. Gov.uk's own registration and UTR guidance is only ever accessed by going directly to gov.uk yourself — HMRC does not ask for your UTR, or any other personal tax details, by unsolicited text message or email link. If a message asking you to "confirm your UTR" or "verify your tax refund" arrives out of the blue, treat the request itself as the warning sign, and go to gov.uk directly rather than following any link it contains.
How ac-co does this
Once you've connected your HMRC account (or entered your UTR manually) inside ac-co, it's stored against your profile and reused automatically for every future filing — you don't re-enter it each tax year, and it's carried through correctly to your SA100 submission rather than being something you have to remember to look up again every January. If you're setting up ac-co for the first time and don't have a UTR yet because you haven't registered with HMRC, that registration step still has to happen with HMRC directly — no filing software, ac-co included, can generate a UTR on your behalf, since only HMRC's own registration process issues one.
Related reading
- Self assessment deadline 2026/27 — the 5 October registration deadline your UTR depends on.
- Self assessment late filing penalty — what happens if a missing UTR delays your filing past a deadline.
- How to get your SA302 — the next document you'll need, once your UTR has let you file.