Self Assessment Deadlines for 2025/26: What to File and When
Key Self Assessment dates for the 2025/26 tax year, including registration, paper filing, online filing, and payment deadlines.
Last reviewed: 23 June 2026
The main 2025/26 dates
The 2025/26 tax year runs from 6 April 2025 to 5 April 2026. Paper Self Assessment returns are normally due by 31 October 2026, while online returns and balancing payments are normally due by 31 January 2027.
If this is your first year needing Self Assessment, registration usually needs attention well before the filing deadline so HMRC can issue the right references.
Payment can matter more than filing
The 31 January deadline is not only a filing date. It is also usually when any balancing tax for the previous tax year is paid, along with the first payment on account where one applies.
Why use an accountant early
An accountant can help identify missing records, estimate the tax bill, check payments on account, and avoid the January rush. Waiting until late January often limits the advice available.