When is the paper Self Assessment deadline?
HMRC must receive a paper tax return for the 2025 to 2026 tax year by 11:59pm on 31 October 2026. Online returns have until 11:59pm on 31 January 2027, and the tax you owe is due by 31 January 2027 whichever way you file.
Checked against GOV.UK on 27 October 2026.
The paper deadline
A paper return for 2025 to 2026 must reach HMRC, not just be posted, by 11:59pm on 31 October 2026.
You can send it any time from 6 April 2026.
Source: Self Assessment deadlines
Filing online instead
Online returns are due by 11:59pm on 31 January 2027.
If you want HMRC to collect what you owe through your PAYE tax code, the online return must be in by 11:59pm on 30 December 2026.
Source: Self Assessment deadlines, Pay your Self Assessment bill through your tax code
Paying the tax
The tax you owe is due by 11:59pm on 31 January 2027, however you file. If you make payments on account, the second is due by 31 July.
Source: Self Assessment deadlines, Payments on account
If a return is late
An initial £100 penalty. After 3 months, £10 a day up to £900. After 6 months, a further 5% of the tax due or £300, whichever is greater, and the same again after 12 months.
Tax paid late adds penalties of 5% of the unpaid tax at 30 days, 6 months and 12 months, plus interest.
Source: Self Assessment penalties
What CWA does for you
We prepare and file your return online, so the paper deadline stops mattering, and tell you what to pay and when.