Self Assessment deadlines and penalties
Tax year 2026/27
The deadlines follow the same pattern every year, set by the end of the tax year on 5 April. Below are the dates for the 2026/27 tax year, and how penalties build up if you file or pay late.
Deadlines for the 2026/27 tax year
The 2026/27 tax year runs from 6 April 2026 to 5 April 2027.
- Register for Self Assessment, if you have not filed before: by 5 October 2027
- Paper return: HMRC must receive it by 11:59pm on 31 October 2027
- Online return: by 11:59pm on 31 January 2028
- Pay the tax you owe: by 11:59pm on 31 January 2028
- To have the bill collected through your tax code, submit online by 11:59pm on 30 December 2027
Late filing penalties
Penalties start as soon as the return is late and grow the longer it stays late: an initial fixed penalty, then daily penalties after 3 months up to a maximum, then further penalties after 6 months and again after 12 months, each based on the tax due or a fixed amount, whichever is greater. GOV.UK sets out the amounts and has a penalty estimator.
Late payment penalties and interest
If you pay late, penalties are added to the tax still unpaid at 30 days, 6 months and 12 months, and interest is charged on the amount owed.
If you had a reasonable excuse
You can appeal against a penalty if you had a reasonable excuse. GOV.UK explains how to appeal.
Common mistakes
- Missing the 5 October registration deadline in your first year of self-employment.
- Filing on time but paying late. Late payment has its own penalties and interest.
Sources
Checked against GOV.UK on 6 November 2026. Rules and figures change, so verify on GOV.UK before you rely on this. General information, not tax advice.