You are responsible for telling HMRC about your income by filing a Self Assessment tax return. There are different ways to register depending on if you are:
Self-employed as a ‘sole trader’ and earning more than £1,000.
A partner in a business partnership
A director of a limited company
If you did not send an online return last year you’ll need to register for Self Assessment as soon as possible. You need to register no later than 5th October after the end of the tax year for which you need to file a tax return. This means, if you need to file a tax return for the last tax year (6 April 2022 to 5 April 2023), you’ll need to register for Self-Assessment by 5th October 2023.
If you’re sending HMRC a paper tax return for the 2022-2023 tax year, the deadline is 31st October 2023. However, if you’re submitting an online tax return, you have a few more months, with a deadline of 31st January 2024. The deadline for paying the tax you owe is also 31st January 2024.
HMRC must receive your tax return and any money you owe by the deadline. If you submit your tax return late or pay your bill late, HMRC will usually charge you a penalty and interest on late payments.