When exactly you need to register

HMRC uses a threshold called the trading allowance to decide whether you need to register. If your gross self-employment income in a tax year (6 April to 5 April) exceeds £1,000, you're required to register for Self Assessment and notify HMRC that you're trading as self-employed.

Note that this is based on your income, not your profit. Even if your costs wipe out your earnings entirely, the £1,000 trigger is based on what you took in, not what you kept.

You also need to register if you:

If your self-employment income is £1,000 or less, you can use the trading allowance to avoid registering entirely — you simply don't declare that income. But once you cross the threshold, registration is not optional.

How to register

Registration is done online through HMRC's Government Gateway service. The process takes around 10 minutes if you have your National Insurance number to hand.

  1. Go to gov.uk and search "register as self-employed"
  2. Sign in to — or create — your Government Gateway account
  3. Complete the short form with your personal details, the date you started trading, and the nature of your work
  4. Submit the registration

Once registered, HMRC will send you a Unique Taxpayer Reference (UTR) number in the post. This is a 10-digit number you'll need every time you file a tax return. Allow up to 10 working days for it to arrive, though it often comes sooner.

Important date: The deadline to register is 5 October following the end of the tax year in which you started trading. So if you started earning self-employment income in the 2024–25 tax year (which ran to 5 April 2025), you had until 5 October 2025 to register.

What if you're already past the deadline?

Register anyway — immediately. HMRC can charge a penalty for late registration, but in practice they apply these inconsistently, and the penalty is usually reduced significantly if you have a reasonable excuse or if the late registration is your first offence. The penalty for failing to notify is calculated as a percentage of the tax owed, so the sooner you register and pay any tax due, the lower the potential charge.

Do not wait until you're "ready" to file your return, and do not assume that because nothing has happened, HMRC hasn't noticed. Late registration with all tax paid is a far better position than no registration at all.

What happens after you register

Once HMRC has your registration, you'll be set up for Self Assessment. You'll receive a letter confirming your UTR and telling you which tax returns you need to file. From that point, you'll need to file a Self Assessment return each year — even in years where you earn very little — until you tell HMRC you've stopped trading.

You'll also need to pay Class 2 National Insurance contributions (a flat weekly amount, currently collected through your Self Assessment bill) and Class 4 NI on profits above a certain threshold. Both are handled through your annual tax return — you don't need to pay them separately during the year.

Common mistake: Many people put off registering because they plan to "do it when they fill in the tax return." The tax return and the registration are two separate things. The return can't be filed without a UTR, and the UTR takes time to arrive. Register the moment you know you'll exceed the £1,000 threshold — don't leave it until January.

A note on being employed and self-employed at the same time

Having a PAYE job doesn't exempt you from registering for self-employment. If you earn more than £1,000 from freelance or side work in a tax year, you need to register for Self Assessment regardless of your employment status. Your employed income and your self-employed income are assessed together to work out your total tax bill, with any PAYE tax you've already paid offset against what you owe.

Getting registered is genuinely straightforward. The process is the same whether you're a freelance designer, a plumber, a dog walker, or a part-time consultant — and it removes the risk of penalties that can grow the longer you leave it.