The main dates fall the same way every year; what changes is the tax year they belong to. Here is every Self Assessment deadline, what each one costs to miss, and the one that catches people who have never filed before.
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For most individual taxpayers, the standard Self Assessment deadlines fall on the same dates each year. The tax year they relate to changes, and different deadlines can apply in some circumstances, for instance where HMRC issues a return late, so check yours rather than assuming the table below is the whole answer. Here are the main Self Assessment deadlines, what they relate to and what can happen if you miss them.
| What | When |
|---|---|
| Tell HMRC you need to file | 5 October after the tax year ends |
| Paper return | 31 October, 11:59pm |
| Online return | 31 January, 11:59pm |
| Pay the tax owed | 31 January, 11:59pm |
| To pay through your tax code instead, if eligible | 30 December |
| Second payment on account | 31 July |
The 30 December row carries conditions, which is why it catches people out. Paying through your tax code is open to you only where you owe less than £3,000, where you already pay tax through PAYE as an employee or on a company pension, and where the online return is in by that date. Miss any one of the three and the tax is due in full on 31 January.
Always check the current position on GOV.UK's Self Assessment deadlines page before you rely on a date, including this one. Deadlines can be moved, and have been.
This is the part that trips people up. That is why a useful Self Assessment article should always make the relevant tax year clear.
A UK tax year runs from 6 April to 5 April. An online return is normally due by the following 31 January, while the standard paper filing deadline is 31 October, so at any given moment you are usually dealing with a year that ended some months ago while living in a year you will report on later.
The cycle currently open, as at August 2026: the 2025/26 tax year, which ran from 6 April 2025 to 5 April 2026. Register by 5 October 2026, file on paper by 31 October 2026, file online and pay by 31 January 2027.
If you are reading this in a later year, the shape is the same and the years move on by one. That is the whole trick to Self Assessment dates. Sole traders and landlords inside Making Tax Digital for Income Tax now also have quarterly deadlines running alongside these.
5 October is the quietest of the deadlines and the one most often missed, because it applies to people who have never filed before and therefore are not expecting a deadline at all.
If you started self-employment, began receiving property income or received other untaxed income, first check whether you need to submit a Self Assessment return. If you do and you are not already registered, the notification deadline is normally 5 October following the end of the tax year.
The 5 October deadline commonly catches people filing for the first time, but it can also apply where someone was previously registered, did not need to file for the previous year, and now needs to reactivate their Self Assessment account.
Registering is not instant. HMRC introduced a new online registration service in September 2026, so check the current GOV.UK registration process rather than leaving registration until January: leaving it that late is how people end up unable to file a return they are ready to file.
Missing 5 October is separate from the £100 late-filing penalty. Late notification can result in a failure-to-notify penalty, depending on the circumstances and on whether tax remains unpaid.
Two deadlines, three months apart, and the earlier one is easy to walk into by accident. A paper return has to be with HMRC by 31 October. Miss it and you cannot simply post it in November; the penalty applies even if you would have been well inside the online deadline.
Filing online buys you until 31 January. Almost everybody should. The exceptions are the handful of situations where the online service cannot handle a particular combination of income, which is worth checking early rather than discovering in October.
Filing and paying share the 31 January deadline, which people reasonably read as one event. They are two, and the second one is where the shock lives.
Payments on account normally apply where your previous year's relevant Self Assessment tax was £1,000 or more and less than 80% of your tax was collected outside Self Assessment, for instance through a tax code. There are normally two payments, each usually equal to half of the previous year's relevant tax bill, due on 31 January and 31 July. Where they do apply, a first profitable year can mean paying a full year's tax and half of the next year's on the same day.
Nobody enjoys that conversation in the third week of January. It is largely avoidable with a set of figures in the autumn, which is one of the reasons we push clients towards knowing where they stand well before the deadline, and why the habit of setting the money aside as it arrives matters more than any amount of January resolve.
Late filing and late payment are penalised separately, so it is possible to be hit by both for the same return.
The penalties below apply to the 2025/26 Self Assessment return due by 31 January 2027. The penalty rules are changing as Making Tax Digital for Income Tax is introduced, so later tax years may be subject to a different regime.
| Late filing | Late payment |
|---|---|
| £100 as soon as the deadline passes, even if no tax is due | 5% of the tax unpaid at 30 days |
| After 3 months: £10 a day, up to £900 | 5% again at 6 months |
| After 6 months: 5% of the tax due, or £300 if greater | 5% again at 12 months |
| After 12 months: another 5% or £300, whichever is greater | Interest runs on top throughout |
HMRC sets the first two out plainly on its own penalties page.
an initial £100 penalty ... after 3 months, additional daily penalties of £10 per day, up to a maximum of £900
The £100 is the one worth dwelling on, because it applies even where there is no tax to pay. A dormant year, a business that made a loss, a return you did not think you needed: all still £100 if the return was due and did not arrive. The daily charge is the one that does the real damage, though. It starts three months late, which for a 31 January deadline is the start of May, and by then most people who are going to forget have long stopped thinking about it. At £10 a day it turns a £100 irritation into a four-figure problem without anybody making a second decision.
It is rarely the filing itself. In our experience the January panic is usually about not having the numbers rather than not having the time, and poor or incomplete bookkeeping is a common cause of avoidable Self Assessment problems.
The pattern is consistent enough to be worth naming:
It is what happens when the only moment anybody looks at the numbers is the moment they are due. Keeping the bookkeeping up to date throughout the year can make preparing the return considerably quicker and reduce the risk of missing information.
File anyway. This is the single most useful thing in this article.
Filing and paying are separate obligations with separate penalties, so not filing because you cannot pay adds a penalty to a problem you already have. File on time, then deal with the payment. Contact HMRC as early as possible if you cannot pay in full: you may be able to agree a Time to Pay arrangement and spread the amount over instalments. Those arrangements are considerably easier to access from a position of having filed than from a position of having gone quiet.
You can normally file from 6 April, once the tax year has ended. The return is not due for nearly ten months, but filing early does not mean paying early: the tax is still due on 31 January.
So an early return buys you the figure without the bill. You find out in May what you owe in January, which is eight months to put it aside rather than eight weeks to find it. That is the whole argument, and it is a better one than most people expect.
HMRC frames it the same way in its annual reminder, and its choice of words is worth noticing.
The countdown to the Self Assessment deadline has begun but there is still time to thoroughly prepare and file an accurate tax return by 31 January.
The word doing the work there is "accurate". HMRC's own framing is that hitting the date is not the difficult part; filing something correct by it is, and the two are easy to confuse when January is close. A return rushed together in the last week meets the deadline and can still cost you, either through relief you did not claim because there was no time to look, or through a figure that has to be amended later. Filing earlier gives you more time to check the figures, resolve missing information and correct errors before the deadline. If you would rather it was simply handled, that is what our tax return service is for.
A paper return is due by 31 October and an online return by 31 January, both at 11:59pm, and the tax is due on 31 January as well. Those dates fall the same way every year; what changes is which tax year they relate to. Always check the current position on the GOV.UK Self Assessment deadlines page.
As at August 2026, the cycle open is the 2025/26 tax year, which ran from 6 April 2025 to 5 April 2026. Register by 5 October 2026, file on paper by 31 October 2026, and file online and pay by 31 January 2027.
5 October after the end of the tax year in which you needed to start filing. It is the quietest of the deadlines and the most often missed. It commonly catches people filing for the first time, but it can also apply where someone was previously registered and now needs to reactivate their Self Assessment account. Registering is not instant, and HMRC introduced a new online registration service in September 2026, so check the current GOV.UK process rather than leaving it until January.
£100 as soon as the deadline passes, even if no tax is due. After three months, daily penalties of £10 up to a maximum of £900. After six months, a further 5% of the tax due or £300 if greater, and the same again at twelve months.
File anyway. Filing and paying are separate obligations with separate penalties, so not filing because you cannot pay adds a penalty to a problem you already have. HMRC has arrangements for spreading a bill, and they are easier to access having filed.
Advance payments towards the following year's bill, due on 31 January alongside the balancing payment and again on 31 July. They are generally not required where last year's tax came to less than £1,000, or where more than 80% of it was already collected at source. Where they do apply, a first profitable year can mean paying a full year of tax and half of the next on the same day, which is where the January shock usually comes from.
Yes. The initial £100 late filing penalty applies where a return was due and did not arrive, whether or not there is any tax to pay. A dormant year or a loss-making year still needs the return filing if HMRC has asked for one.
Filing early does not mean paying early: the tax is still due on 31 January. So an early return gives you the figure without the bill, which can mean eight months to set the money aside rather than eight weeks to find it.
Every figure on this page was checked against the sources above on . Rates and thresholds change. If you are reading this long afterwards, check the current position before you act on it.
If you are unsure what needs reporting, want your return prepared, or need help getting the bookkeeping ready first, tell us where you are up to. We will explain what is needed before any work begins.
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