If you work for yourself, you need to tell HMRC. This guide explains when and how to register for Self Assessment, and what you will need.
Published July 2026 · Updated July 2026
You must register for Self Assessment once your income from self-employment goes over £1,000 in a tax year (the 'trading allowance'). The deadline is 5 October following the end of that tax year.
You register online through HMRC. You will set up a Government Gateway account, give some details about your business, and HMRC will issue your Unique Taxpayer Reference (UTR), the number you need to file.
Have your National Insurance number, contact details, and the date you started trading to hand. Once registered, keep records of all income and allowable expenses from day one.
Each year you file a Self Assessment return and pay any tax by 31 January. As Making Tax Digital for Income Tax phases in, you will also keep digital records and send quarterly updates once your income crosses the threshold.
You can be employed and self-employed at once. You register for Self Assessment for the self-employed part; your employment is taxed separately through PAYE.
A Unique Taxpayer Reference, a 10-digit number HMRC gives you. You need it to file your Self Assessment return.
Register as soon as you can. Penalties can apply, but they are usually smaller if you put it right promptly and pay what you owe.
This guide is general information for UK small business owners, not accounting, tax or legal advice. Rules, rates and thresholds reflect 2026/27 and change over time; always check the linked official source or a qualified adviser for your situation.