Starting to work for yourself is exciting. Registering with HMRC is not, but it's not as complicated as many people assume either. The key is knowing when to register, how to do it, and what to expect once you have. This guide walks through the whole process in plain English.
When do you need to register?
You need to register as self-employed if you earn more than £1,000 from self-employment in a tax year. This £1,000 is the trading allowance — income below this can usually be ignored for tax purposes, but once you cross it, HMRC needs to know about you.
The registration deadline is 5 October following the end of the tax year in which you started trading. So if you began working for yourself during the 2025/26 tax year (which runs from 6 April 2025 to 5 April 2026), you need to register by 5 October 2026.
In practice, I'd always recommend registering sooner rather than later — ideally as soon as you start earning self-employed income. Waiting until close to the deadline creates unnecessary stress, and if you miss it, HMRC may issue a late registration penalty.
How to register
Registration is done online through the HMRC website. Go to gov.uk and search for "register self-employed" or navigate to the Self Assessment registration section. You'll need to set up or log into a Government Gateway account — if you've never had one, you'll create one as part of the process.
During registration you'll be asked for your National Insurance number, your date of birth, your contact details, and some basic information about your business — mainly the nature of your trade (e.g., "web design", "plumber", "freelance writer") and the date you started trading.
The whole process takes about 20 minutes if you have everything to hand. There's no fee — it's completely free to register.
What is a UTR number?
Once you've registered, HMRC will send you a Unique Taxpayer Reference — your UTR number. This is a 10-digit number that identifies you for tax purposes and is separate from your National Insurance number. You'll use your UTR number every time you file a Self Assessment tax return, and if you ever have cause to contact HMRC about your tax affairs, they'll ask for it.
Your UTR arrives by post, typically within 10 working days. It will come on a letter addressed to you from HMRC — not on a card, just a standard letter. Keep it somewhere safe because you'll need it every year.
One thing that catches people out: HMRC's online system won't let you file a return until your UTR is set up, so if you're approaching the filing deadline and haven't registered yet, you may not have enough time to receive your UTR and complete your return. Don't leave it late.
What about National Insurance?
As a self-employed person, you pay two classes of National Insurance. Class 4 NI is calculated as a percentage of your profits and is paid through Self Assessment along with your income tax — for 2026/27 this is 6% on profits between £12,570 and £50,270, and 2% above that. Class 2 NI was historically a flat weekly charge but was abolished for most self-employed people from April 2024. Those with profits above the Small Profits Threshold (£6,845 for 2026/27) receive Class 2 NI credits automatically, which protects your State Pension record.
If your profits are below the Small Profits Threshold but above £1,000, you can make voluntary Class 2 contributions to protect your State Pension and benefit entitlements — this is generally worth doing as the cost is low relative to the benefit.
What records do you need to keep?
HMRC requires you to keep records of all your self-employed income and expenses. There's no prescribed format — a spreadsheet, an accounting software package, or even organised paper receipts are all acceptable — but you must be able to back up the figures you put on your Self Assessment return.
You're legally required to keep business records for at least five years after the 31 January filing deadline for that tax year. So records for the 2025/26 tax year (filed by 31 January 2027) must be kept until at least 31 January 2032. HMRC can enquire into your returns within this period and will expect to see supporting records.
In practice, keeping digital records is increasingly the sensible approach — easier to search, harder to lose, and you'll need them digitally anyway when Making Tax Digital for Income Tax applies to you.
Filing your first return
Your first Self Assessment tax return will cover the period from when you started trading to 5 April at the end of that tax year. You'll file it online by 31 January the following year. So if you started trading in October 2025, your first return covers October 2025 to 5 April 2026 and is due by 31 January 2027.
The return is where you declare your income, claim your expenses, and calculate your tax bill. If this is new to you, it's worth spending time understanding what expenses you can claim — getting this right can make a significant difference to your bill. Our guide on sole trader expenses covers the main categories in detail.
One more thing
Registering is the easy part. The harder bit is keeping your bookkeeping in order throughout the year so that filing your return doesn't become a January panic. Set aside time each month — even just an hour — to record income received and expenses paid. Future you will be very grateful.