When is the Self Assessment tax return deadline?
Short answer
31 January following the end of the tax year for online returns, which is also the payment deadline. Paper returns are due by 31 October. If it is your first return you must register with HMRC by 5 October — a deadline that comes four months earlier and is the one most people miss.
Verified · 4 cited sources
The UK tax year runs from 6 April to 5 April. For the year ending 5 April 2026, first-time filers must register by 5 October 2026, paper returns are due by 31 October 2026, and online returns and payment are due by 31 January 2027.
The registration deadline is the one that catches people. Registering produces a Unique Taxpayer Reference, posted to you, and then an activation code for online services, also posted. That two-step postal process takes time, which is why leaving registration until January is a genuine problem rather than an inconvenience.
The £100 late filing penalty applies immediately once the deadline passes, whether or not any tax is owed. After three months, daily penalties accrue. Further penalties apply at six and twelve months, calculated on the tax due. Late payment carries separate penalties and interest.
Penalties can be appealed where there is a reasonable excuse — serious illness, a bereavement, a genuine HMRC service failure. Being busy, finding the system difficult, or relying on an accountant who did not file are not reasonable excuses.
If HMRC has sent you a notice to file, you must file even if you believe no tax is due, unless HMRC formally withdraws the notice. A great many £100 penalties arise this way.
- Tax year: 6 April to 5 April
- Register by 5 October if it is your first return
- Paper returns: 31 October
- Online returns and payment: 31 January
- £100 penalty applies immediately, even if you owe nothing
People also ask
Sources & provenance
Facts verified
- 1.Self Assessment tax returns: deadlines OfficialUK GovernmentUsed for: Registration, paper and online deadlines
- 2.Register for Self Assessment OfficialUK GovernmentUsed for: 5 October registration deadline and the UTR process
- 3.Self Assessment penalties OfficialUK GovernmentUsed for: Penalty schedule and reasonable excuse appeals
- 4.If you cannot pay your tax bill on time OfficialUK GovernmentUsed for: Time to Pay arrangements
All deadlines and penalty rules come from the GOV.UK pages cited. The observation that the 5 October registration deadline is the one most people miss is our emphasis rather than an HMRC statement. Deadlines shift by one day where a due date falls on a weekend or bank holiday in some circumstances — check GOV.UK if you are close to one.
Facts on this page are taken from the sources listed above — UK government departments, devolved administrations, regulators, statutory bodies and official statistical releases. Comparisons, judgements and "which option suits whom" conclusions are AI-assisted analysis written over those sources; they are marked in the text and listed as an AI-analysis entry in the sources, not attributed to any authority. Rates, thresholds, fees and processing times change, usually at the start of a tax year in April; figures are current as at the review date shown and should be confirmed with the responsible body before you rely on them. Much of what follows differs between England, Scotland, Wales and Northern Ireland — where it does, this site says so.