How to Register as a Sole Trader in the UK

Who needs to register

You need to register as self-employed with HMRC if any of the following apply:

• You earned more than the £1,000 trading allowance from self-employed work in a tax year (the tax year runs 6 April to 5 April).
• You want to claim tax-free childcare, maternity allowance or other benefits based on self-employment.
• You want to pay voluntary Class 2 National Insurance to protect your State Pension entitlement.
• You need to prove you're self-employed (for mortgages, for instance).

You do not need to register if your self-employed income is below £1,000 in the tax year — the trading allowance covers it. But if you're trading regularly and expect to grow, registering anyway is sensible.

The deadlines that matter

The headline deadline is 5 October following the end of the tax year in which you started trading. For example: if you started self-employed work in May 2025 (within the 2025/26 tax year ending 5 April 2026), you must register by 5 October 2026.

That said — register earlier. Your UTR can take up to two weeks to arrive by post, and you can't file your tax return without it. Leaving it until the last possible date is one of the most common reasons people miss the 31 January filing deadline and pay an avoidable £100 fine.

What you'll need before you start

How to register, step by step

1. Go to GOV.UK and search for "register for Self Assessment". Choose the "self-employed" option.
2. Create a Government Gateway account if you don't already have one. You'll need an email address and will create a User ID and password.
3. Complete the SA1 / CWF1 form online. CWF1 is the specific form for new self-employed registrations and is the one most people need.
4. Enter your business details: what you do, your business start date and your expected turnover (a rough estimate is fine).
5. Submit and wait. Your UTR arrives by post within about 10 working days. You'll also receive an activation code for your Government Gateway business tax account.

If you've previously been in Self Assessment (for example, as a landlord or higher-rate taxpayer), you already have a UTR — you don't need a new one. Just add self-employment to your existing record.

What happens after you register

HMRC will issue your UTR and (separately) your online services activation code. Keep both safe — you'll need the UTR for everything tax-related, including any future correspondence with HMRC or your accountant. Once registered, you're on the Self Assessment system and will need to file a return every year until you tell HMRC you've stopped trading.

You'll also typically be enrolled for Class 2 National Insurance, paid alongside your Income Tax bill once your profits cross the Small Profits Threshold.

Your first tax return

Self Assessment returns cover a full tax year (6 April to 5 April). The return must be filed online by 31 January following the end of the tax year, and any tax due must be paid by the same date. If your tax bill exceeds £1,000, you'll also be asked to make payments on account — advance payments towards next year's tax, due 31 January and 31 July.

Set aside roughly 25–30% of your profit in a separate savings account as you earn it, and you won't be surprised in January. Our monthly finance review checklist includes a tax-saving prompt.

Common mistakes to avoid

• Waiting until the deadline. Register in week one of trading, not month nine.
• Losing the UTR letter. Photograph it. Save it in a password manager. You will need it.
• Forgetting Class 2 NI. Voluntary contributions can protect your State Pension if your profits are low.
• Mixing personal and business money. Open a separate account from day one — see our separation guide.
• Not saving for tax. A 25–30% rule covers most basic-rate taxpayers; higher earners need more.