A UTR is the ten-digit Unique Taxpayer Reference HMRC gives you when you are set up for Self Assessment, and you cannot file a return without one. It is not something you apply for on its own: you register for Self Assessment, and the UTR arrives by post as a consequence, which is why the answer to how to get a UTR number is really an answer about registering and about how long the post takes. This page covers what a UTR is for, which registration route applies to you, how long each step takes, and the deadline that decides whether you are late.
A UTR is issued by registering, not by asking for one
There is no form that produces a UTR by itself. You tell HMRC that you have income to report, and HMRC opens a Self Assessment record and issues the reference against it. The route differs by why you are registering: newly self-employed people register as self-employed, which also sets up Class 2 and Class 4 National Insurance, while somebody with untaxed savings, foreign income or a property letting registers for Self Assessment without registering a trade. Both produce the same ten-digit reference; only the form differs, and choosing the wrong one is the usual reason a registration is bounced back.
How long it takes, and why that matters more than the form
The reference itself is generated quickly, but it is posted, and the activation code for the online account is posted separately. Plan on weeks rather than days, and on longer around January when everybody else is doing the same thing. That lag is the practical reason to register as soon as you know you will have to file rather than when the return is due: the filing deadline does not move because your UTR has not arrived, and a return cannot be filed without it. If you have registered and the reference has not come, chase it before the deadline rather than after.
The deadline is 5 October after the tax year, not 31 January
Registration for Self Assessment is due by 5 October following the end of the tax year in which the income arose. So income earned in the year ending 5 April must be registered by the 5 October that follows, six months later, even though the return itself is not due until the 31 January after that. People who discover Self Assessment in January are usually already late on registration even though they are early on filing. Registering late does not remove the obligation to file and it does not move the filing date.
Finding a UTR you already have
If you have filed before, the reference is on any previous return, on a notice to file, on a statement of account, and inside your HMRC online account. It does not change and it is not reissued, so a lost UTR is a lookup rather than a new registration. Registering a second time because the number cannot be found creates a duplicate record, which is far more trouble to unpick than finding the original.
Questions people ask about how to get a utr number
How long does a UTR number take to arrive?
Weeks rather than days, because it is posted, and longer in the run-up to the January deadline. Register as soon as you know you will need to file; the filing deadline does not move to accommodate the post.
Can I file a return without a UTR?
No. The return is filed against the Self Assessment record the UTR identifies, so there is nothing to file against until it exists. That is why the registration deadline sits six months ahead of the filing deadline.
Is a UTR the same as a National Insurance number?
No. A National Insurance number identifies you for contributions and benefits and you keep it for life. A UTR identifies a Self Assessment record and is issued when that record is opened. You will usually be asked for both when registering.
I registered last year and stopped trading. Do I need a new UTR?
No. The reference stays with you. If you start trading again you tell HMRC the record is active once more; you do not register from scratch, and doing so creates a duplicate.