What is a UTR number in the UK?

A UTR (Unique Taxpayer Reference) is a permanent 10-digit number HMRC issues when you register for Self Assessment. It identifies your personal tax record and must appear on every Self Assessment return, tax payment and correspondence with HMRC about your income tax affairs.

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

Register for Self Assessment online via HMRC's Government Gateway using the CWF1 form for self-employment. HMRC will send your UTR by post to your registered address within 10 working days. You must register by 5 October following the end of the first tax year in which you were self-employed.

Where can I find my UTR number if I have lost it?

Your UTR appears on any previous Self Assessment tax return, your HMRC 'Notice to File' letter, and your Self Assessment statements. You can also retrieve it instantly by logging into your HMRC Personal Tax Account at gov.uk/personal-tax-account without needing to call HMRC.

Does my UTR number change if I stop being self-employed?

No. Your UTR is permanent. If you close your Self Assessment record and later re-register, HMRC reactivates the same 10-digit number. You never receive a new UTR, regardless of gaps in self-employment or changes of address.

What happens if I file my Self Assessment without a UTR number?

You cannot submit a Self Assessment return without a valid UTR. If you have not yet received yours, you must wait for HMRC to issue it by post or retrieve it online. Delays in obtaining a UTR that push your filing past 31 January can trigger a £100 automatic late-filing penalty.

Can I find my UTR number online without calling HMRC?

Yes. Log in to your HMRC Personal Tax Account at gov.uk/personal-tax-account. Under the Self Assessment section you will see your UTR displayed on the dashboard. You will need your Government Gateway user ID and password.

Is a UTR number the same as a Company Registration Number?

No. A Company Registration Number (CRN) is issued by Companies House when a limited company is incorporated. A UTR is issued by HMRC for tax purposes. A limited company has both a CRN and its own UTR, separate from the director's personal UTR.

Do I keep the same UTR if I stop being self-employed and then start again?

Yes. Your UTR is permanent and tied to you personally. If you deregister from Self Assessment and later re-register, HMRC reactivates the same 10-digit number rather than issuing a new one.

Is it safe to share my UTR number?

You should only share it with HMRC, a registered accountant or tax agent, or trusted financial institutions that require it for legitimate purposes such as a mortgage application. Treat it like your bank sort code: not completely secret, but not something to broadcast carelessly.

What Is a UTR Number? Unique Taxpayer Reference Explained

HMRC posts your UTR to you within 10 working days of registering for Self Assessment, yet thousands of newly self-employed people spend months hunting for it, delaying their first tax return and occasionally triggering automatic late-filing penalties. That single piece of mail is arguably the most important letter a freelancer or sole trader will ever receive from HMRC.

Key takeaways

Your UTR is a permanent 10-digit number that never changes, even if you stop and restart self-employment.
You cannot file a Self Assessment tax return without it.
HMRC issues it by post within 10 working days of you registering; you can also retrieve it via your Personal Tax Account.
Sole traders, company directors, landlords and anyone in a partnership each need their own UTR.
Keep it private: sharing it unnecessarily is a data-security risk.

What does a UTR number actually look like?

A UTR is exactly 10 digits, for example 1234567890. HMRC sometimes writes it with a trailing K (1234567890K) on older correspondence, but the 10-digit number is what you enter on forms and software. It is sometimes labelled "Tax Reference" on letters, which trips people up. You will also find a separate 13-character reference (your UTR followed by the tax year, such as 123456789012345) used on payment slips, but the core identifier is always the 10 digits.

Digits in every UTR

Working days to receive it by post

31 Jan

Online SA filing deadline

Who needs a UTR and who does not?

You need a UTR if any of the following apply to you:

You are self-employed as a sole trader and earned more than £1,000 in a tax year (the trading allowance threshold).
You are a company director taking dividends or salary outside PAYE.
You own rental property and receive income that must be declared.
You are in a business partnership (each partner has their own UTR; the partnership also has a separate one).
You earn over £100,000 and HMRC requires you to file a return regardless of employment status.
You have capital gains to report, for example from selling shares or a second property.

Employees paid entirely through PAYE with no other income sources generally do not need a UTR. Their tax is handled through their employer and their tax code rather than Self Assessment.

Personal Tax Account: A secure HMRC online service where individuals can view their UTR, check income and tax history, update contact details and manage Self Assessment without calling HMRC.

How to get a UTR number: the three routes

Register for Self Assessment online

The most common route is HMRC's online registration. You create a Government Gateway account, complete the SA1 form (or CWF1 if you are registering as self-employed for National Insurance at the same time), and HMRC posts the UTR to your registered address. The 5 October deadline in your second year of self-employment is the legal cut-off for registration if you started earning self-employed income after 5 April that same tax year. Miss it and you risk a penalty.

Retrieve an existing UTR

If you have filed before and lost your number, it is printed on:

Document	Where the UTR appears
SA100 tax return	Top right of every page
HMRC "Notice to file" letter	Header section
Previous Self Assessment statements	Reference field
Personal Tax Account (online)	Dashboard, under "Self Assessment"

Log in at gov.uk/personal-tax-account to find it instantly rather than waiting on the HMRC phone line, which can involve lengthy hold times.

Call HMRC

If you cannot access your Personal Tax Account, HMRC's Self Assessment helpline (0300 200 3310) can confirm your UTR after verifying your identity. Have your National Insurance number, date of birth and address to hand.

UTR vs National Insurance number: what is the difference?

These two identifiers confuse a lot of people. Your National Insurance number (format: AB 12 34 56 C) tracks your NI contributions and state pension entitlement throughout your life. Your UTR is purely a tax-filing reference. A mortgage application or job offer typically asks for your NI number; an accountant or tax software always asks for your UTR. You will need both as a self-employed person, but they do different jobs.

A worked example: Priya registers as a sole trader

Priya leaves her job in August 2025 and begins freelancing as a graphic designer. She earns £22,000 in the 2025/26 tax year. Her obligations run as follows:

Registration deadline: 5 October 2026 (the October after the end of the tax year in which she started).
HMRC posts her UTR: She registers in September 2025 and receives her UTR by mid-October 2025.
Filing deadline: 31 January 2027 for an online Self Assessment return covering 2025/26.
Tax owed: Priya uses the TapTax sole trader tax calculator to estimate her Income Tax and Class 4 National Insurance before the deadline.

Without her UTR, Priya cannot submit the return on her own account or instruct an accountant to file on her behalf. The UTR is, quite literally, the key to the system.

What happens if you file without registering in time?

Late registration does not automatically produce a penalty on its own, but it delays issuing your UTR, which in turn can push your filing past the 31 January deadline. A late return triggers an immediate £100 fixed penalty, then £10 per day after three months, up to £900. If you are exploring Self Assessment for the first time, registering early is the single highest-leverage action you can take to avoid unnecessary charges.

For broader guidance on navigating the self-employment tax landscape, the TapTax blog covers everything from allowable expenses to payment on account in plain English.

Your UTR is not just an admin formality; it is the foundation of your entire Self Assessment record, and HMRC cannot process a single return without it.

TapTax, UK tax glossary