UTR Number Explained: What It Is, How to Get One from HMRC

A UTR number (Unique Taxpayer Reference) is a 10-digit number that HMRC assigns to identify you for tax purposes in the UK. If you're self-employed, a CIS subcontractor, or a landlord, you need a UTR number to file Self Assessment tax returns, register for CIS, and sign up for Making Tax Digital.

This guide explains what a UTR is, how to get one, where to find it if you've lost it, and why it matters for your tax affairs.

What Is a UTR Number?

A Unique Taxpayer Reference (UTR) is a 10-digit number issued by HMRC to every individual or organisation registered for Self Assessment or Corporation Tax. It's sometimes simply called your "tax reference" on HMRC letters.

Your UTR is permanent — it stays the same for life, even if you stop being self-employed and restart later. It's different from your National Insurance number, which is used for employment and benefits.

What a UTR looks like: A 10-digit number, often displayed in groups (e.g., 12345 67890). It contains only numbers — no letters.

Who gets one:

• Sole traders registered for Self Assessment
• CIS subcontractors registered with HMRC
• Landlords registered for Self Assessment
• Partners in a business partnership (each partner gets their own, plus the partnership gets a separate one)
• Limited companies (a company UTR, separate from any personal UTR)

When Do You Need a UTR Number?

You'll use your UTR in several key situations:

• Filing Self Assessment — you need it to log in and submit your tax return
• CIS verification — contractors need your UTR to verify your CIS registration with HMRC
• Signing up for MTD — Making Tax Digital registration requires your UTR
• Contacting HMRC — they'll ask for it to identify you
• Appointing an accountant — your accountant needs your UTR to act on your behalf

Without a UTR, you cannot file a Self Assessment return or register for CIS at the 20% deduction rate.

How to Get a UTR Number

You get a UTR by registering for Self Assessment with HMRC. There's no separate UTR application — the number is generated automatically when you register.

Step 1: Check If You Need to Register

Use HMRC's online tool at Check if you need to send a Self Assessment tax return on GOV.UK. You typically need to register if you:

• Are self-employed and earned more than £1,000 (2025/26)
• Have rental income
• Need to pay Capital Gains Tax
• Have untaxed income from other sources

Step 2: Register Online

Go to Register for Self Assessment on GOV.UK. You'll need:

• Your National Insurance number
• Your name, date of birth, and address
• Your business start date (if self-employed)
• A Government Gateway account (create one during registration if you don't have one)

The online registration takes about 15 minutes. For a detailed walkthrough, see our guide on how to register for Self Assessment.

CIS subcontractors: When registering, select that you work as a subcontractor in the construction industry. This registers you for both Self Assessment and CIS at the same time.

Step 3: Wait for Your UTR to Arrive

After you register, HMRC sends your UTR by post to your registered address. This typically takes up to 15 days. If you're based overseas, it can take longer.

You'll also receive an activation code for your HMRC online account in a separate letter.

Important timing: The registration deadline is 5 October following the end of the tax year in which you started earning. If you register late, you won't receive a penalty for late registration itself, but you may face penalties for late filing if your UTR arrives too late for you to file on time.

How to Find a Lost UTR Number

You can find a lost UTR number through your Personal Tax Account on GOV.UK, on previous HMRC correspondence, or by calling HMRC directly. Here are all the options:

Online

• Personal Tax Account — sign in at GOV.UK using your Government Gateway credentials. Your UTR is displayed on your account homepage.
• HMRC app — download the HMRC app and sign in to view your UTR.

On Documents

Your UTR appears on:

• Previous Self Assessment tax returns (form SA100)
• HMRC notices to file a return
• Payment reminders from HMRC
• Your Self Assessment statement
• Letters about payments on account

Look for a 10-digit number, often labelled "Unique Taxpayer Reference" or simply "Tax Reference."

By Phone

If you can't find it anywhere, call HMRC's Self Assessment helpline on 0300 200 3310 (Monday to Friday, 8am to 6pm). They'll verify your identity and provide your UTR over the phone. Have your National Insurance number ready.

UTR vs National Insurance Number: What's the Difference?

These two numbers serve different purposes and are often confused:

	UTR	National Insurance Number
Format	10 digits (numbers only)	2 letters + 6 digits + 1 letter (e.g., AB123456C)
Issued by	HMRC (on registration)	HMRC/DWP (usually at age 16)
Purpose	Tax returns, CIS, Self Assessment	Employment, benefits, state pension
Who has one	Anyone registered for Self Assessment	Everyone with the right to work in the UK
Changes	Permanent — same for life	Permanent — same for life

You need both numbers for Self Assessment. Your NI number links your tax record to your National Insurance contributions, while your UTR identifies you within the Self Assessment system.

Common UTR Number Questions for Self-Employed

I'm a CIS subcontractor — do I get a different UTR?

No. Your UTR is the same whether you use it for Self Assessment, CIS, or both. When you register as a CIS subcontractor, HMRC activates your existing UTR within the CIS system. You give this same UTR to every contractor you work for.

How long does it take to get a UTR?

HMRC typically sends your UTR by post within 15 days of registration. Plan ahead — if you register close to the filing deadline, your UTR may not arrive in time to submit your return. You can register online at any time of year.

Can I start working before my UTR arrives?

Yes. As a self-employed person, you can start working immediately. You don't need your UTR to begin trading — only to file your tax return later. However, if you're a CIS subcontractor, contractors will deduct at the higher 30% rate until your UTR arrives and they can verify your registration.

Do I need a new UTR if I stop and restart self-employment?

No. Your UTR is permanent. If you stop being self-employed and later start again, you use the same UTR. You may need to re-register for Self Assessment, but HMRC reactivates your existing UTR rather than issuing a new one.

Frequently Asked Questions

What happens if I file without a UTR?

You cannot file a Self Assessment return without a UTR — the online system requires it to identify your account. If your UTR hasn't arrived yet, you'll need to wait or call HMRC to chase it.

Can I share my UTR with someone?

Your UTR is not secret in the same way a password is, but treat it with care. You'll share it with your accountant, HMRC, and (if you're a CIS subcontractor) your contractors. However, don't share it publicly or with anyone who doesn't need it for legitimate tax purposes.

Is a UTR the same as a tax code?

No. A UTR is your unique reference for Self Assessment. A tax code (like 1257L) tells your employer how much tax-free income to apply to your salary. They're different systems — you can have both if you're employed and self-employed at the same time.

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This guide is for informational purposes only and does not constitute tax, legal, or financial advice. Tax rules change frequently. Always verify current requirements on GOV.UK or consult a qualified accountant for your specific situation.

Official Sources

• Find your UTR number - GOV.UK
• Register for Self Assessment - GOV.UK
• Check if you need to send a Self Assessment tax return - GOV.UK
• Self Assessment tax returns - GOV.UK