How to register as a sole trader with HMRC: step-by-step guide for 2025/26

If you start working for yourself, HMRC needs to know who is responsible for reporting the income. For most new one-person businesses, that means registering as self-employed and filing a Self Assessment tax return.

When you need to register

Register with HMRC if you are trading as an individual and your self-employed income is more than the trading allowance, or if you need to pay tax and National Insurance through Self Assessment. You may be a sole trader even if you only work part-time, freelance alongside a PAYE job, or invoice one client at a time.

For the 2025/26 tax year, the key registration deadline is 5 October 2026. That is the deadline to tell HMRC you need Self Assessment for income earned between 6 April 2025 and 5 April 2026. Registering earlier is safer because HMRC has to issue your Unique Taxpayer Reference before you can file.

Step 1: create or sign in to a Government Gateway account

HMRC online services use a Government Gateway user ID. If you already have one from PAYE, VAT, Child Benefit, or another government service, you may be able to use it. If not, create a new Government Gateway account and keep the user ID somewhere secure.

HMRC may ask for identity checks, address history, National Insurance number, and contact details. Use details that match official records; mismatches can slow down registration.

Step 2: register for Self Assessment as self-employed

The sole trader registration route is HMRC's online Self Assessment registration for self-employed people. Historically, the underlying form was known as CWF1. Online registration asks for broadly the same information: when you started trading, what the business does, your personal details, and how HMRC should contact you.

Use the date you genuinely began trading. That is usually when you started offering services, invoicing customers, or buying stock with the intention to sell, not necessarily the day you first thought about the business.

Step 3: wait for your UTR

After registration, HMRC issues a Unique Taxpayer Reference, usually called a UTR. This is a 10-digit reference used on your Self Assessment account and tax return. Keep it safe: accountants, software, and HMRC calls may ask for it.

Do not leave registration until January. You may need time for the UTR to arrive, for online services to activate, and for your records to be ready before filing.

Step 4: keep records from day one

Once you are trading, keep records of sales, expenses, invoices, mileage, bank statements, and receipts. You do not need a complicated system at the start, but you do need a system you can explain later. A spreadsheet is enough for many small businesses if it separates income, allowable expenses, and personal spending clearly.

Step 5: estimate tax before your first deadline

Registering is only the start. Your first real risk is spending money that should be saved for Income Tax, Class 4 National Insurance, and possibly payments on account. Once you have a rough profit figure, run the self-employed tax calculator and then read our payments on account guide so January does not arrive as a surprise.

Common registration mistakes

Waiting until January, then discovering you still need a UTR.
Assuming side income does not count because tax is already taken from a PAYE job.
Using turnover as if it were profit when estimating the tax bill.
Not keeping evidence for expenses claimed on the first return.
Forgetting the 5 October registration deadline after the tax year ends.

What to read next

Once registered, move on to our beginner's guide to Sole Trader Self Assessment and the 2025/26 HMRC dates calendar.

Official source

For the live HMRC registration service, use GOV.UK: Register for Self Assessment if you are self-employed.