When is the Self Assessment deadline for 2025 to 2026?
For the 2025 to 2026 tax year, HMRC must receive an online return and any tax you owe by 11:59pm on 31 January 2027. Paper returns are due by 31 October 2026. If you make payments on account, the second one is due by 31 July.
Checked against GOV.UK on 27 October 2026.
The dates
Paper return: 11:59pm on 31 October 2026.
Online return, if you want the tax collected through your tax code: 30 December 2026.
Online return and payment of tax owed: 11:59pm on 31 January 2027.
Second payment on account: 31 July.
Source: Self Assessment deadlines
If you are new to Self Assessment
You must tell HMRC by 5 October if you need to complete a return for the previous year and have not sent one before. If you register after 5 October 2026, HMRC gives you a new filing deadline, but the tax is still due by 31 January 2027.
Source: Self Assessment deadlines
If you miss the deadline
A late return brings an initial £100 penalty, followed by daily penalties and further charges the longer it is late. Interest is charged on tax paid late. Send the return as soon as you can: the penalties keep growing.
Source: Self Assessment penalties
What CWA does for you
We prepare and file your return, tell you what to pay and when, and send reminders well before each date.