When is the tax year?
In the UK, people get taxed on what they earn from 6 April to the following 5 April.
So for example, the 2022/23 tax year runs from 6 April 2022 to 5 April 2023.
If you are employed and not a high earner (£100k a year+, or £50k a year if you get child benefit), you don't need to do anything beyond that as your employer would have taken off your tax.
If you are self-employed, you will need to complete a tax filing, called a tax return (don't confuse the word return with refund though - most people have to pay!).
The filing needs to be completed by 31 January after the tax year ends. So for the year ended 5 April 2021, the filing was due by 31 January 2022. If you have earned more than the personal allowance (which is around £12,500 depending on the year), you will need to pay tax as well. Some people put money aside as they earn.
Normally, if you submit after the deadline you'd be liable to a £100 penalty. However, for 2021/22 HMRC did not charge a late filing penalty if you filed online by 28 February 2022. A small amount of interest could still have been charged from 1 February 2022.
We always recommend that people complete a tax return as soon as possible. The quickest and easiest way to do this is with untied.