Your UTR number is the reference HMRC uses to match every Self Assessment return, payment and letter to you. Without it you can’t file a tax return, an accountant can’t act for you, and a payment can end up on the wrong account. The number itself is easy to find once you know where to look. The trouble usually starts when people mix it up with a different reference, or register too late to get one before the deadline.
This guide covers what a UTR is, who needs one, the four places to find yours, how long a new one takes, and what to do if you’ve lost it.
What is a UTR number?
UTR stands for Unique Taxpayer Reference. It is a 10-digit number HMRC issues when you register for Self Assessment or when a limited company is set up. HMRC letters sometimes just call it your “tax reference” or “reference”, which is part of why people struggle to spot it.
Your personal UTR stays with you for life. If you stop filing returns and later start again, HMRC reactivates the same number rather than issuing a new one.
Who needs a UTR number?
You need a personal UTR if you have to file a Self Assessment tax return. That includes:
- Sole traders with self-employed income over the £1,000 trading allowance
- Landlords with rental income above the £1,000 property allowance
- Company directors whose dividends or other untaxed income mean they must file
- Partners in a business partnership
- Anyone else HMRC asks to file, for example because of foreign income or capital gains
Not sure if you’re one of them? Our guide to whether you need to file a Self Assessment walks through 12 common situations.
Personal UTR vs company UTR: the common mix-up
A limited company gets its own UTR for Corporation Tax. As a director you will usually have two: one for the company and one for you personally if you file a Self Assessment return. Both are 10 digits, so they look identical at a glance.
- Personal UTR — used on your Self Assessment return and payments
- Company UTR — used on the company’s CT600 Corporation Tax return
Using the company UTR on your personal return, or the other way round, is one of the most common reasons a return is rejected or a payment goes missing. Label both clearly wherever you store them.
A UTR is also different from your National Insurance number (two letters, six digits, one letter), your VAT number (9 digits) and your Companies House company registration number (usually 8 characters).
Where to find your UTR number
If you’re an individual or sole trader, HMRC says you can find your UTR in four places:
- Your Personal Tax Account on GOV.UK — sign in and open the Self Assessment section.
- The HMRC app — the quickest route if you already have the app set up.
- Your welcome letter — the SA250 “Welcome to Self Assessment” letter you received after registering.
- Any HMRC Self Assessment document — previous tax returns, notices to file, statements and payment reminders.
If an accountant has filed for you before, they will also have it on file. A short email to them is often the fastest fix.
Finding a company’s UTR
For a limited company, check previous Corporation Tax returns and HMRC letters. If you can’t find it, you can request the company’s UTR online. HMRC will post it to the company’s registered office address at Companies House, so make sure that address is current and someone checks the post there.
How long does it take to get a UTR number?
HMRC says you’ll usually get your UTR by post around 15 days after you register, and longer if you live overseas. In practice it can take longer during busy periods, especially in the weeks before the 31 January filing deadline.
That’s why the registration deadline matters. If you started a business or received new untaxed income, you must register by 5 October after the end of the tax year. Leave it until January and you may not get your UTR in time to file by 31 January. You’d then face a late filing penalty even though you were trying to comply. Our step-by-step registration guide shows exactly how to register online.
Lost your UTR number? What to do
- Check the HMRC app and your Personal Tax Account first. This works if you can still sign in.
- Search your paperwork and email. Look for any HMRC letter about Self Assessment, or a copy of an old return.
- Ask your accountant if one has filed for you.
- Contact HMRC’s Self Assessment helpline. You’ll need to pass security checks, usually including your National Insurance number. HMRC will post the UTR to the address it holds for you — not read it out — so update your address first if you’ve moved.
Keep your UTR safe
Your UTR is not as sensitive as a bank password, but it is a key part of your tax identity. Criminals use it in scam emails and texts claiming to offer a tax refund. HMRC will not email or text you about a refund with a link to claim it. Share your UTR only with HMRC, your accountant and anyone you trust who genuinely needs it, such as a mortgage lender checking your tax records.
Do you need a UTR to use an accountant?
Yes. An accountant uses your UTR to get authorised as your agent with HMRC and to file your return. If you’re registering for the first time, an accountant can’t file until your UTR arrives, but they can prepare everything in the meantime so the return goes in as soon as the number lands.
At SmartFiling, our ICAEW chartered accountants prepare and file Self Assessment tax returns for a fixed fee from £149. If you have your UTR — or you’re waiting for it — get a free quote and we’ll reply within one working day.
Frequently asked questions
Is my UTR the same as my tax code?
No. Your tax code (for example 1257L) tells your employer how much tax to deduct under PAYE. Your UTR is only used for Self Assessment.
Can I file a tax return without a UTR?
No. HMRC needs your UTR to accept a Self Assessment return, which is why registering early matters.
Does my UTR ever change?
No. Your personal UTR stays the same for life, even if you stop and restart Self Assessment.
