# Self Assessment deadlines and penalties

Canonical: https://taxmo.co.uk/self-assessment-guide/deadlines-and-penalties
Tax year: 2026/27
Part of: [Self Assessment topics](https://taxmo.co.uk/self-assessment-guide)

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

- [GOV.UK, Self Assessment tax returns: deadlines](https://www.gov.uk/self-assessment-tax-returns/deadlines)
- [GOV.UK, Self Assessment tax returns: penalties](https://www.gov.uk/self-assessment-tax-returns/penalties)
- [GOV.UK, Estimate your penalty for late Self Assessment tax returns and payments](https://www.gov.uk/estimate-self-assessment-penalties)

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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.