What is Self Assessment?
If you’re employed by another person or company, your tax will usually be sorted for you by your employer. However, if you work for yourself, or have income outside of your main job, you may need to let us know what money you’ve made.
You do this by completing something called a Self Assessment tax return. We’ll explain who needs to do one, and how to do it.
Who needs to do one?
Self Assessment is a way we collect any tax you owe that can’t be collected
through your employer. Each year, you’ll need to let us know your income by
filling in a tax return. You may need to do one if you:
- are self-employed
- are in a business partnership
- have to pay Capital Gains Tax on something you sold for a profit
You may also need to do one if you have untaxed income from things like:
- renting out a property
- tips and commissions
- savings, investments and dividends
- money coming in from another country
Doing a tax return might sound a bit scary, but don’t worry. There’s a lot of help and support if you need it.
Key thing to remember:
If you’re not sure whether you need to do a Self Assessment tax return, check for yourself using our online tool on GOV.UK.
Making Tax Digital for Income Tax
If you’re a sole trader or make money from property, the way you send us information about your income is changing. It’s called Making Tax Digital for Income Tax. For some people that change starts from April 2026.
If you use Making Tax Digital for Income Tax, things work differently from Self Assessment. You should check if the different rules apply to you on GOV.UK.
What you need to do
Most people only need to send us a Self Assessment tax return once a year.
The tax year runs from 6 April to 5 April each year, so the 2025 to 2026 tax year started on 6 April 2025 and ends on 5 April 2026.
Key thing to remember:
You can send us your online tax return any time between 6 April 2026 and 31 January 2027, but the sooner you do it, the better.
You’ll need to:
- Check if you need to do a tax return.
- If you do, register for Self Assessment. If you’ve already registered before, but didn’t send a tax return last year, reactivate your account.
- Set yourself up for our online services. If you haven’t already got an account, you can set one up on GOV.UK.
- Gather info on your income, capital gains and expenses to help you do your online tax return.
- Send us your online tax return and make any payments on or before 31 January. The deadline for paper returns is on or before 31 October.
Helpful tip:
You may prefer to do an online tax return. It’s easier to correct if you make a mistake, the sums are all done for you automatically, you can be sure we’ve got it by the deadline, and there’s help every step of the way.
Many people also get a professional, such as an accountant or tax agent, to deal with us on their behalf. You can find out more on GOV.UK.
You need to register first
If you’ve never done a tax return before, you’ll need to register with us. You can find out how to register on GOV.UK.
If you’ve completed a tax return before, but didn’t complete one last year, then you’ll just need to reactivate your account.
Key thing to remember:
If you do need to do a tax return, make sure you let us know on or before 5 October after the first tax year you might owe tax for. So, for the 2025 to 2026 tax year, you’ll need to register or reactivate your account on or before 5 October 2026. If you don’t do this, you could get a fine.
When you register, we’ll send you a Unique Taxpayer Reference (UTR). This 10-digit number will go on every tax return you do in the future, so we know it’s from you. Keep it somewhere safe when you get it.
Key thing to remember:
You can always find your UTR number online on GOV.UK. You can also use the HMRC app. Find out how to download it on GOV.UK.
A few key dates
As long as you understand and stick to a few key dates, it’s easy to stay on track.
You need to:
- register for Self Assessment on or before 5 October
- make sure we get your paper tax return on or before 31 October
- send us your online tax return and pay any tax you owe on or before 31 January
- pay your full bill on or before 31 July if you choose to spread the cost (these are called ‘payments on account’)
Helpful tip:
Of course, you can do all these things earlier. In fact, the sooner you send your tax return, the more time you’ll have to plan how to pay any tax you might owe and avoid any penalties. It also means that if we find you’ve paid too much tax, you’ll get a refund sooner.
Self Assessment is different from Simple Assessment
With ‘Simple’ Assessment, you don’t need to do a tax return. We’ll simply get in touch to let you know how much tax you owe, as well as how and when you need to pay it.
Their similar names mean a lot of people get these two confused, but they’re actually very different.
This is because we already have information from your employers, banks, and the Department for Work and Pensions, so we can work out what tax you owe. You can find out more on our Simple Assessment page.
Help is available if you need it
We want you to feel tax confident. Here are some helpful info and videos to help you get up to speed:
If you’re worried about paying your tax bill on time, you may be able to spread the cost by setting up a weekly or monthly payment plan with us. You can also get extra support if your health condition or personal circumstances make it difficult when you contact us. Find out more on GOV.UK.