What is the Self Assessment deadline for 2025/26?

For the 2025/26 tax year (6 April 2025 to 5 April 2026):

• Register for Self Assessment (if first time): 5 October 2026
• File a paper return: 31 October 2026
• File online and pay any tax owed: 31 January 2027
• Second payment on account for 2024/25: 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.