When is the deadline to register for Self Assessment?

5 October after the end of the tax year in which you went over £1,000. For income earned between 6 April 2026 and 5 April 2027, the deadline is 5 October 2027, and the return and payment are due by 31 January 2028.

Can I be employed and self-employed at the same time?

Yes. Your job carries on being taxed through PAYE, and you report your side-hustle income separately on a Self Assessment tax return. The side-hustle profit is taxed on top of your salary.

Does it cost anything to register as a sole trader?

No. Registering for Self Assessment is free and done online on GOV.UK. You do not need to set up a limited company.

Hamster blog

Do I need to register as self-employed for a side hustle?

Published 1 October 2026 · Figures are for the 2026–27 tax year

The short answer

Yes, once your side hustle brings in more than £1,000 in a tax year (6 April to 5 April), even if you also have a full-time job taxed through PAYE. You register for Self Assessment with HMRC as a sole trader by 5 October after the tax year ends. If you earn £1,000 or less, you do not need to register.

The £1,000 rule

HMRC says you must register for Self Assessment as a sole trader if you earn more than £1,000 from self-employment in a tax year. Below that, the trading allowance covers your income and you do not need to do anything.

Three things about that £1,000:

It is your income before expenses, not your profit.
It is all your side hustles added together, not £1,000 each.
It has nothing to do with your job. A salary taxed through PAYE does not count towards it, and having a job does not remove the need to register.

Selling your own unwanted belongings does not count either, because that is not trading. See tax on Vinted, eBay and Depop sales for where that line sits.

The deadlines

You do not register the moment you pass £1,000. The deadline is 5 October after the end of the tax year in which you did.

For income earned in the 2026–27 tax year (6 April 2026 to 5 April 2027):

5 October 2027: register for Self Assessment
31 January 2028: file your online tax return and pay what you owe

If you went over £1,000 in 2025–26, the registration deadline was 5 October 2026. If you missed it, register as soon as you can: the return and payment for that year are still not due until 31 January 2027.

What registering involves

Registering is free and done online on GOV.UK. HMRC then sends you a Unique Taxpayer Reference (UTR), a 10-digit number you use to file your return.

You do not need a limited company, a business bank account or an accountant to be a sole trader. Your job is unaffected: it carries on being taxed through PAYE, and you report the side hustle separately once a year.

HMRC also lists two reasons to register even if you are under £1,000: you made a loss and want to claim relief for it, or you want to pay voluntary Class 2 National Insurance towards your State Pension.

What you will pay

Registering does not create a bill by itself. You pay tax on your profit: your side-hustle income minus either your expenses or the £1,000 trading allowance, whichever is larger.

That profit sits on top of your salary. For 2026–27:

Income Tax: if your job already uses your £12,570 Personal Allowance, your profit is taxed at 20%, or 40% once your total income passes £50,270.
Class 4 National Insurance: 6% on self-employed profit between £12,570 and £50,270, and 2% above. A side hustle making less than £12,570 profit pays none.

So a side hustle that makes £2,500 of profit alongside a £30,000 job costs £500 in Income Tax and no National Insurance.

Larger side hustles: Making Tax Digital

If your self-employment and property income together are above £50,000, HMRC's Making Tax Digital for Income Tax applies from 6 April 2026, with quarterly updates through software instead of one annual return. The threshold falls to £30,000 from April 2027 and £20,000 from April 2028. Most side hustles are well below this.

Keeping track

The awkward part is that the £1,000 line and the 5 October deadline are easy to pass without noticing. Hamster is a free Android app that totals your side-hustle income through the tax year and keeps the figures for your return in one place. With Premium, it alerts you the moment you cross £1,000 and exports your figures ready for your return.

Quick answers

Do I need to register as self-employed for a side hustle?: Yes, if your side-hustle income is more than £1,000 in a tax year, even if you have a full-time job. You register for Self Assessment as a sole trader by 5 October after the tax year ends. At £1,000 or less you do not need to register.
When is the deadline to register for Self Assessment?: 5 October after the end of the tax year in which you went over £1,000. For income earned between 6 April 2026 and 5 April 2027, the deadline is 5 October 2027, and the return and payment are due by 31 January 2028.
Can I be employed and self-employed at the same time?: Yes. Your job carries on being taxed through PAYE, and you report your side-hustle income separately on a Self Assessment tax return. The side-hustle profit is taxed on top of your salary.
Does it cost anything to register as a sole trader?: No. Registering for Self Assessment is free and done online on GOV.UK. You do not need to set up a limited company.

Sources

This is general information, not personal tax advice. Rules and rates change — check the linked GOV.UK pages or speak to an accountant about your own situation.