Filing Your Self-Assessment
The UK tax year runs from the 6th April to the 5th April the following year. The filing and payment deadline for the tax year is 31st January after the end of the tax year.
For example, for the tax year 6th April 2021 - 5th April 2022, you would need to file your self-assessment and pay your taxes by 31st January 2023.
It is also possible to file your self-assessment by paper, the deadline for this is 31st October.
If you are filing for the first time you should register for self-assessment by 5th October after the end of the tax year.