If you're starting out in UK construction — or if you've been working on sites for years and never sorted your tax properly — there's one number that unlocks everything: your UTR.

UTR stands for Unique Taxpayer Reference. It's a 10-digit number that HMRC assigns to you when you register for Self Assessment. Think of it as your tax ID — it links everything you do with HMRC to one record: your tax returns, your CIS registration, your refunds, your payments.

Without a UTR, you can't register for CIS. Without CIS registration, your contractor deducts 30% from every payment instead of 20%. And without filing Self Assessment (which requires your UTR), you can't claim any of that money back.

What Exactly Is a UTR Number?

A UTR is a 10-digit number that HMRC issues when you register for Self Assessment. It's unique to you — no one else has the same number — and it stays with you permanently. It never changes, even if you change your name, address, or business structure.

Your UTR is not the same as your National Insurance number. Your NI number identifies you for National Insurance contributions and benefits. Your UTR identifies you specifically for tax — Self Assessment, CIS, Corporation Tax (for companies). You need both, and they serve different purposes.

Why CIS Subcontractors Can't Work Without One

If you work in construction as a subcontractor, your UTR is the foundation of everything:

• CIS registration requires it — you can't register for CIS without a UTR. And without CIS registration, contractors deduct 30% instead of 20% from every payment
• Contractors need it to verify you — when a contractor hires you, they check your UTR with HMRC to confirm your registration status and deduction rate
• Self Assessment requires it — you can't file your tax return without your UTR, and you can't claim your CIS refund without filing
• Your SA302 is linked to it — the income proof document that mortgage lenders require is generated from your Self Assessment, which is tied to your UTR
• Gross payment status requires it — if you want 0% deductions, your GPS application is processed against your UTR record

✓ No registration required  ·  100% Free  ·  HMRC 2026/27 Aligned

How to Get a UTR Number — Step by Step

Online (Fastest Route)

1. Go to gov.uk and search for "register for Self Assessment".
2. Create a Government Gateway account if you don't have one — you'll need your name, email address, and a phone number for verification.
3. Select the reason for registering — for most CIS subcontractors, this is "self-employed" or "not self-employed but need to file a return".
4. Complete the registration form with your full name, National Insurance number, date of birth, address, and details about your self-employment (trading name, what you do, when you started).
5. Submit the form — HMRC processes it and sends your UTR by post within 10 working days.
6. You'll also receive a separate activation code by post within 7 working days — use this to activate your online tax account.

By Post (If You Can't Register Online)

If you can't use the online service, download and complete form SA1 (for individuals) from gov.uk and post it to HMRC. Allow several weeks for processing — online registration is significantly faster.

For Limited Companies

When you incorporate a limited company through Companies House, HMRC automatically registers it for Corporation Tax and issues a company UTR. This is separate from your personal UTR. The company UTR typically arrives by post within a few weeks of incorporation. If it hasn't arrived after 3 weeks, call the Corporation Tax helpline on 0300 200 3410.

What You Need to Apply

I've Lost My UTR — How to Find It

Your UTR doesn't change. If you had one before, you still have the same number — you just need to find it. Here's where to look:

1. HMRC Personal Tax Account — log in via Government Gateway and check the Self Assessment section. Your UTR is displayed there.
2. HMRC App — download the HMRC app and log in. Your UTR appears in the Self Assessment area.
3. SA250 welcome letter — the original letter HMRC sent when you first registered. If you kept it, your UTR is at the top.
4. Previous tax returns — any Self Assessment you've filed will show your UTR on the front page.
5. HMRC correspondence — payment reminders, notices to file, and statements of account all include your UTR.
6. Call HMRC — if none of the above work, call the Self Assessment helpline on 0300 200 3310. They'll verify your identity and can tell you your UTR over the phone or send it by post.

UTR vs NI Number vs Government Gateway — What's the Difference?

Three numbers, three purposes. Here's how they differ:

Contractors need your UTR and NI number to verify you for CIS. Your Government Gateway ID is just your login — you never share it with anyone.

The Registration Deadline You Might Not Know About

HMRC requires you to register for Self Assessment by 5 October following the end of the tax year in which you first earned self-employed income. For example, if you started subcontracting in the 2025/26 tax year (6 April 2025 to 5 April 2026), you must register by 5 October 2026.

Missing this deadline doesn't prevent you from registering — HMRC still processes late registrations — but it can trigger penalties if the late registration causes a late tax return. The sooner you register, the sooner you get your UTR, and the sooner you can register for CIS and start being deducted at 20% instead of 30%.

What Happens After You Get Your UTR

Once your UTR arrives, here's your immediate to-do list:

1. Activate your online tax account — use the activation code from HMRC's second letter (arrives within 7 working days, valid for 28 days).
2. Register for CIS — this is a separate step from getting your UTR. Without it, contractors deduct at 30%. Our CIS registration guide walks you through it.
3. Give your UTR and NI number to every contractor — they need both to verify you with HMRC before making any payments.
4. Start keeping records — every invoice, every CIS deduction statement, every expense receipt. You'll need them when you file your Self Assessment.

Your UTR Checklist

• Register for Self Assessment at gov.uk as soon as you start self-employed work
• Wait for your UTR to arrive by post (10 working days)
• Activate your online tax account using the separate activation code
• Save your UTR somewhere permanent — phone, cloud, password manager
• Register for CIS using your UTR — separate step, takes 10 minutes
• Give your UTR and NI number to every contractor you work for
• File your Self Assessment by 31 January each year using your UTR
• Keep your UTR confidential — only share it with HMRC, your accountant, and contractors