When Do You Have to Register for Self Assessment?

You must register for Self Assessment if you earn more than £1,000 from self-employment, or have other untaxed income like rental or significant savings interest. The deadline to register is 5 October after the tax year, with online returns due by 31 January.

Last reviewed: 30 May 2026 · 2 min read

Key Facts

Register if self-employment income tops £1,000 a year
Registration deadline is 5 October after the tax year ends
Online tax returns are due by 31 January

Who needs to register

Self Assessment is how HMRC collects tax that isn't taken automatically through PAYE. You'll usually need to register if you earn over £1,000 from self-employment or a side hustle, receive rental income, have large untaxed savings or dividend income, or earn over a certain amount and have other tax to sort out.

If all your income is from a salary taxed through PAYE, you generally don't need to file. It's the extra, untaxed income that triggers it.

The deadlines that matter

Miss these and penalties follow. You must register by 5 October following the end of the tax year in which you had the income. Paper returns are due by 31 October, and online returns — what most people file — by the following 31 January, which is also when any tax owed must be paid.

Late filing brings an automatic £100 penalty even if you owe no tax, rising the longer you leave it, so it pays to register and file in good time.

FAQ

Frequently Asked Questions

Do I need to do a tax return for a small side hustle? +

Only if you earn more than £1,000 from it in a tax year. Below that, the trading allowance covers you and there's nothing to file. Above £1,000, you must register for Self Assessment, report the income and pay tax on the profit above the allowance.

What happens if I register for Self Assessment late? +

You can face penalties, particularly if it means you file your return or pay your tax late. There's an automatic £100 fine for a late return even with no tax due, and further charges build up over time. Registering as soon as you know you need to avoids the problem.

Can I do my own tax return or do I need an accountant? +

Most people with straightforward income — a side hustle or some freelance work — can complete Self Assessment themselves online through gov.uk. An accountant is more useful if your finances are complex. Keeping good records of income and expenses throughout the year makes filing far easier either way.

Topics covered

tax self assessment side hustle

This article is for informational purposes only and does not constitute financial advice. Always do your own research or speak to a qualified financial adviser before making financial decisions.