What is the Self Assessment deadline for 2025/26?

For the 2025/26 tax year (6 April 2025 to 5 April 2026): the deadline to register for Self Assessment if you haven't before is 5 October 2026; the deadline to file a paper return is 31 October 2026; the deadline to file online and pay any tax owed is 31 January 2027. If you also have payments on account to make, the second payment on account for 2024/25 is due 31 July 2026. Missing any of these deadlines can result in penalties and interest, so it's worth getting your return filed well in advance. We can file as soon as the tax year ends on 5 April, so there's no need to leave it to January.