One myth we hear a lot from new sole traders: you need a UTR number before you can start trading. You don’t. You need one to file your first Self-Assessment tax return, and you need to register with HMRC in good time to get it, but the trading itself can start the moment you’re ready.

There’s a second myth worth busting too – that this reference and your National Insurance number are interchangeable. They’re not, and mixing the two up on a form is one of the more common reasons a registration gets delayed. If you’re a sole trader wondering what it actually is, how to get one, or what to do if you’ve lost yours, here’s everything you need to know.

What is a UTR number?

A UTR, or Unique Taxpayer Reference, is a 10-digit code that HMRC issues when you register for Self-Assessment or set up a limited company. It might appear on paperwork simply labelled ‘tax reference’, but it’s the same thing. Every sole trader, partnership and limited company has one, and you’ll need to quote yours whenever you contact HMRC, file a Self-Assessment return, or register for the Construction Industry Scheme (CIS) as a subcontractor.

If you already work under CIS, you may recognise this reference as the one contractors ask to verify before your first payment – our guide to the Construction Industry Scheme (CIS) for builders covers this in more detail. Unlike your National Insurance number, it’s issued once and stays with you for life, even if you stop trading and start again years later.

How do I get a UTR number as a sole trader?

There’s no separate application form. You get one automatically as soon as you register for Self-Assessment with HMRC as a sole trader. To register, you’ll need:

☐  Your National Insurance number

☐  Your date of birth and current address

☐  The date your self-employment started

☐  A brief description of what your business does

 

How to register for a UTR number

You can register online at gov.uk, and the process itself takes around ten minutes. If your circumstances mean you can’t use the online form, you can post a paper CWF1 form to HMRC instead. Either way, the deadline to register is 5 October following the end of the tax year in which you started trading, so if you began trading anytime between 6 April 2025 and 5 April 2026, you’ll need to register by 5 October 2026. Miss it, and you risk a penalty even if you don’t end up owing any tax.

If you’ve already registered for Self-Assessment for a different reason, such as declaring rental income, you’ll usually still need to register again specifically as a sole trader. This also sets you up for Class 2 National Insurance and State Pension purposes. Our guide on what changes when you move from PAYE to self-employment covers this transition in more detail.

How long does it take to arrive?

HMRC posts it to your registered address, usually within around 15 days of registering, though it can take longer if you live overseas. There’s no way to speed this up and no digital short-cut, so it’s worth registering as early as possible rather than leaving it until close to the 5 October deadline, particularly if you also need time to activate your Self-Assessment online account and file your first return by the following 31 January.

I’ve lost my UTR number – what do I do?

If you’ve registered before, it doesn’t disappear, but it’s worth keeping it somewhere easily accessible. Before contacting HMRC, check:

☐  Your Personal Tax Account or the HMRC app – it’s usually displayed there instantly once you’re logged in

☐  Previous Self-Assessment tax returns or HMRC letters, such as notices to file a return or payment reminders

☐  Correspondence from your accountant, if you have one

If none of these turn it up, you’ll need to contact HMRC directly. They won’t read the number over the phone for security reasons, so be prepared to verify your identity and wait for it to arrive by post again. For a quick way to check going forward, our guide to using the HMRC app covers exactly what else you can see and do from your phone.

Getting yours sorted early

Getting it in place is one of the simplest parts of becoming a sole trader, but leaving it too late can hold up everything else, from filing your first tax return to registering for CIS if you’re moving into construction subcontracting.

If you’re just starting out and want a hand getting your registration right first time, contact Adams Accountancy today on 01322 250001 or get in touch online.

About the author

Michelle Adams is a qualified accountant and director at Adams Accountancy, a friendly accountancy practice based in Dartford, Kent. With over 15 years of experience helping sole traders across Kent and beyond, Michelle believes no question is too silly when it comes to getting the basics of your tax setup right from day one.

Frequently asked questions about UTR numbers

Do I need a UTR number before I start trading as a sole trader?

No, you can start trading before you have a UTR number. You just need to register for Self-Assessment, which generates your UTR number, by 5 October following the end of the tax year in which you started trading.

Is a UTR number the same as a National Insurance number?

No, they’re different. Your National Insurance number tracks your NI contributions and State Pension record, while your UTR number links specifically to your Self-Assessment and tax records with HMRC.

Can I use my UTR number for CIS as well as Self-Assessment?

Yes, the same UTR number is used across your CIS registration and your annual Self-Assessment tax return. Contractors will usually ask to verify it before making your first payment under the scheme.

What happens if my UTR number letter never arrives?

If it hasn’t arrived within around 15 days of registering, check your Personal Tax Account or the HMRC app first, as your UTR number is often displayed there before the letter arrives. If you still can’t find it, contact HMRC’s Self-Assessment helpline to have it reissued.