Self Assessment deadlines: what you must send, and when
For the 2025 to 2026 tax year — which started on 6 April 2025 and ended on 5 April 2026 — HMRC must receive your online tax return and any money you owe by 11:59pm on 31 January 2027. If you file on paper instead, HMRC must receive it by 11:59pm on 31 October 2026.
There are two earlier dates that catch people out. If you want your Self Assessment bill collected through your tax code, your online return has to be in by 11:59pm on 30 December 2026. And if you have never sent a return before, you were meant to tell HMRC you needed to complete one by 5 October.
Missing the filing deadline triggers an initial £100 penalty, and the charges escalate the longer a return is outstanding. The table and penalty figures below come from HMRC's own guidance, linked at the foot of the page.
Last checked 21 October 2026 · GOV.UK sources
The deadlines
| Action | Deadline |
|---|---|
| Tell HMRC you need to complete a tax return, by registering for Self Assessment | 5 October |
| Send a paper tax return | 11:59pm on 31 October 2026 |
| Submit an online return, if you want to pay your bill through your tax code | 11:59pm on 30 December 2026 |
| Submit an online tax return | 11:59pm on 31 January 2027 |
| Pay the tax you owe | 11:59pm on 31 January 2027 |
| Second of your payments on account, if you make payments towards your bill | 31 July |
The 5 October deadline applies if you have either not sent a tax return before, or registered before but did not need to send a return for the 2024 to 2025 tax year.
If you register after 5 October 2026, HMRC will send you a letter or email with a different deadline to send your return by — three months from the date on that letter or email. You must still pay the tax you owe by 11:59pm on 31 January 2027 or you will get a penalty.
Trustees of a registered pension scheme and non-resident companies cannot file online. HMRC must receive a paper return from them by 31 January 2027.
If your partnership's accounting date falls between 1 February and 5 April and one of your partners is a limited company, the deadline for online returns is 12 months from the accounting date, and for paper returns 9 months from the accounting date.
HMRC says you can send your return any time on or after 6 April 2026, as long as it arrives by the deadline. If you do not know your profit for the whole tax year, you still need to send a return.
What missing them costs
If you send your tax return late
- An initial £100 penalty.
- After 3 months, additional daily penalties of £10 per day, up to a maximum of £900.
- After 6 months, a further penalty of 5% of the tax due or £300, whichever is greater.
- After 12 months, another 5% or £300 charge, whichever is greater.
- All partners will be charged a penalty if a partnership tax return is late.
If you pay your tax late
- A penalty of 5% of the tax unpaid at 30 days.
- A further 5% of the tax unpaid at 6 months.
- A further 5% of the tax unpaid at 12 months.
- You will also be charged interest on the amount owed.
If you registered for Self Assessment late
- If you register after 5 October and do not pay all of your tax bill by 31 January, you may get a 'failure to notify' penalty.
- That penalty is based on the amount still left to pay.
- You will receive it within 12 months after HMRC receives your Self Assessment tax return.
- A penalty must be paid within 30 days of the date on the penalty notice.
- If you have a reasonable excuse, you can appeal against a penalty.
What to weigh
The options, and who each is not for
Filing it yourself
Suits:
- One straightforward income source, with records already in order.
- A return you have filed before and recognise, with nothing new in the year.
- Enough time before the deadline to stop and check anything you are unsure of.
Not for:
- A first return where you are not confident what has to be declared.
- A year with several income sources, a capital gain, or foreign income.
- Anyone who has left it to the last week and is working from incomplete records — that is where mistakes and missed reliefs happen.
Using an accountant
Suits:
- A first return, or a year that is materially different from the last one.
- Several income streams, a property, a disposal, or anything you would otherwise guess at.
- Wanting someone else to carry the deadline, when yours is already full.
Not for:
- A simple return you have filed confidently before — the fee may well exceed anything it saves you.
- Anyone leaving it until late January and expecting to be taken on; practices fill up before the deadline.
- Someone whose records are not yet gathered. An accountant needs the same paperwork you do, and cannot invent it for you.
Frequently asked
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Every deadline, penalty and rule on this page is taken from these GOV.UK pages, read on 21 October 2026.