How to Get a Self-Employed Tax Code From HMRC

To get the self-employed equivalent of a tax code from HMRC, you register for Self Assessment as a sole trader and HMRC issues you a Unique Taxpayer Reference, a ten-digit number known as a UTR. That number replaces the PAYE tax code your employer would have used and identifies you for every Self Assessment return and payment from that point on. Registration is free, done on GOV.UK, and the UTR arrives by post about 15 days later.

Why There’s No PAYE Tax Code for Sole Traders

Employees get a code like 1257L (the standard for 2025 to 2026) that tells their employer how much income tax to withhold from each paycheck.¹ When you work for yourself, there is no employer running that calculation, so HMRC doesn’t issue you a PAYE code. You calculate and pay your own tax through Self Assessment, and the UTR is the number that links everything together.

The UTR stays with you permanently. If you stop trading for a few years and start again, the same number applies. It is separate from your National Insurance number, which tracks benefits and pension contributions rather than tax filings. Without a UTR you cannot submit a return or pay a Self Assessment bill, and accountants and some clients will ask for it to confirm you are properly registered.

Who Needs to Register

You must register for Self Assessment as a sole trader if your gross self-employment income for a tax year (6 April to 5 April) exceeds £1,000.² That £1,000 figure is the trading allowance; at or below it, you generally do not need to tell HMRC.³

You still need to register below that threshold in specific situations: if you want to claim Tax-Free Childcare based on self-employment income, pay voluntary Class 2 National Insurance to protect your State Pension, claim Maternity Allowance, or get tax relief on a loss.³ Construction Industry Scheme subcontractors and share fishers register regardless of income.²

If you were previously registered for Self Assessment for another reason, such as rental income, you still need to register again specifically as a sole trader.²

What You Need Before You Start

Have everything below to hand before opening the form, because you will need it in one sitting:

Your National Insurance number. If you don’t have one, apply for it separately before you begin.
Your full legal name, date of birth, and current address, matching what HMRC already holds.
A phone number and email address for ongoing HMRC communications.
The date your self-employment started, meaning the day you began trading, not the day you decided to register. This determines which tax year your first return covers.
A specific description of your work, such as “freelance graphic designer” or “mobile hairdresser.” Vague descriptions can prompt HMRC to come back with questions.
Your business address. If you work from home, your home address is fine.

How to Register on GOV.UK

Registration is done online. Go to the “Register for Self Assessment” page on GOV.UK and choose the sole trader option.⁴ The form will prompt you to create Government Gateway sign-in details if you do not already have them.⁵ Those credentials become your login for every future interaction with HMRC, from filing returns to checking what you owe.

Once you submit the registration, HMRC processes the information and generates your UTR.

When Your UTR Arrives

The UTR typically arrives by post within about 15 days, longer if you live overseas.⁶ The letter also contains an activation code you enter into your online account to unlock the full Self Assessment services. Until you activate the account, you cannot file a return or view your tax position online.

Register as early as possible after you start trading. Postal delays during busy periods can leave you without a UTR when you need to file, and there is no way to speed up the letter.

The Registration Deadline

You must tell HMRC about your self-employment by 5 October following the end of the tax year in which you started trading.⁷ If you began freelancing in November 2025 (inside the 2025 to 2026 tax year), your registration deadline is 5 October 2026.

Registering late can trigger a penalty and compresses the time you have to file.² If you do register after 5 October, HMRC will write with a revised filing deadline, usually three months from the date of the letter. The payment deadline does not move: any tax owed is still due by 31 January.⁷

What Happens After You’re Registered

Once you have your UTR and have activated your online account, you file a Self Assessment tax return every year you’re self-employed. Two deadlines apply for each tax year:

31 October, for a paper return.
31 January the following year, for an online return and for paying the tax you owe.

For the 2024 to 2025 tax year, that means an online return by 31 January 2026 or a paper return by 31 October 2025.⁷ Most people file online, so 31 January is the date that matters in practice. Your income tax and Class 4 National Insurance are calculated together when you submit the return.

Finding a UTR You’ve Already Been Issued

If you have registered before, HMRC does not issue a new UTR. Your existing number can be found in a few places:

Your Personal Tax Account or the HMRC app, where the UTR appears once you log in. It may be labelled “reference,” “UTR,” or “official use.”⁶
Previous HMRC correspondence, including old tax returns, payment reminders, notices to file, and statements of account. The ten-digit number appears on all of them.⁶
The Self Assessment helpline on 0300 200 3310, Monday to Friday, 8am to 6pm. HMRC will verify your identity before giving out the number.⁸

Check your email archives as well. If you registered online, the confirmation may reference the number, which is quicker than calling.

1
GOV.UK. Understanding Your Employees Tax Codes
2
GOV.UK. Register as a Sole Trader
3
GOV.UK. Tax-Free Allowances on Property and Trading Income
4
GOV.UK. Check How to Register for Self Assessment
5
GOV.UK. HMRC Online Services: Sign in or Set Up an Account
6
GOV.UK. Find Your UTR Number
7
GOV.UK. Self Assessment Tax Returns – Deadlines
8
GOV.UK. Self Assessment – General Enquiries