What is a UTR number? A guide for the self-employed

Somebody asks for your UTR and you freeze. You know it's a tax thing. You're fairly sure you've got one somewhere. So what is a UTR number, and why does everyone want it?

A UTR is a Unique Taxpayer Reference. GOV.UK describes it as a 10-digit number, sometimes called a "tax reference". HMRC uses it to find your Self Assessment record. Think of it as your account number with the tax office.

What do you use a UTR for?

You need it to file your Self Assessment tax return. You also give it to some customers, mostly businesses, who want proof you're a registered sole trader. Some construction contractors ask for it. Banks and accountants sometimes ask too.

It's not the same as your National Insurance number. Your National Insurance number follows you for life. Your UTR belongs to your Self Assessment account.

How do you get a UTR number?

You get one when you register for Self Assessment. GOV.UK's registration page says you must tell HMRC by 5 October 2026 if you need to send a return for the 2025 to 2026 tax year and either haven't sent one before, or registered before but didn't need to send a return for 2024 to 2025.

If you missed that date, register anyway. The page says "if you tell HMRC after 5 October 2026, you could get a penalty." It doesn't give an amount for registering late. Waiting only makes it worse.

Not sure whether you need to register at all? GOV.UK's sole trader page says you must register as a sole trader if you earn more than £1,000 in a tax year. I explain that rule in do I need to register as self-employed.

The steps are short:

1. Check on GOV.UK that you need to send a return.
2. Start the registration online and answer the questions about your work.
3. Wait for HMRC to post your UTR.

How long does a UTR take to arrive?

GOV.UK says you usually get a new UTR by post about 15 days after registering. It takes longer if you live overseas.

That's why I'd register early. Say you're a dog walker who started in June and made £3,000 by the end of the tax year. If you register in the first week of January, your UTR might not land before you want to file. You can still file, but you'll be waiting on a letter with the deadline getting closer.

What if you've lost your UTR?

First, look in these places. GOV.UK lists your Personal Tax Account, the HMRC app, and older HMRC paperwork such as tax returns, notices to file and payment reminders.

If it's not in any of those, you contact HMRC. For Self Assessment, GOV.UK gives the helpline as 0300 200 3310, open Monday to Friday, 8am to 6pm, and closed on bank holidays. From abroad it's +44 161 931 9070. The page doesn't say how long a replacement takes, so don't leave it until the last week.

One thing to watch. A limited company has a different number, a Corporation Tax UTR, and HMRC posts that to the address registered at Companies House. If you're a sole trader, that doesn't apply to you.

Why getting it sorted early saves you money

Your UTR is the first step towards filing on time. GOV.UK's penalties page says a late return costs an initial £100. After 3 months you add £10 a day, capped at £900. At 6 months and again at 12 months, there's a further charge of 5% of the tax due or £300, whichever is higher.

Paying late has its own penalties. They're 5% of the unpaid tax, charged at 30 days, 6 months and 12 months, plus interest.

The dates for the 2025 to 2026 tax year, per GOV.UK's deadlines page, are:

• Paper return: 31 October 2026
• Online return: 31 January 2027
• Payment of the tax you owe: 31 January 2027
• Return filed by 30 December 2026 if you want the tax collected through your tax code

If you've never filed, you've got time for the online deadline. But only if you get your reference sorted now. For a refresher on saving the money to pay, see how to save for tax.

My take

A UTR is dull until the day you need it, and then you need it quickly. Put it somewhere you can find it. A note on your phone is fine. Add the Self Assessment helpline number while you're there.

At Vcents we're building a way to run your payments from WhatsApp, so the money side of a small business sits in one chat. The tax number is still on you, but fewer loose ends makes it easier to remember where everything is.

Sources

• GOV.UK: Find your Unique Taxpayer Reference (UTR), checked 31 October 2026
• GOV.UK: Register for Self Assessment, checked 31 October 2026
• GOV.UK: Set up as a sole trader, checked 31 October 2026
• GOV.UK: Self Assessment deadlines, checked 31 October 2026
• GOV.UK: Self Assessment penalties, checked 31 October 2026
• GOV.UK: Self Assessment helpline, checked 31 October 2026