The 31 January tax return deadline

What is actually due on 31 January

Three separate things land on the same date, and people often think there is only one.

The first is the return itself. That is the form telling HMRC what you earned and what you are claiming. The second is the balancing payment, which is the tax you still owe for the tax year that ended the previous 5 April. The third, for most people who owe more than £1,000, is the first payment on account towards the year you are currently in.

Take Daniel, a self employed electrician. On 31 January 2027 he files his 2025/26 return showing tax of £5,000. He has already paid £2,000 in payments on account during the year, so his balancing payment is £3,000. On top of that he owes a first payment on account of £2,500 towards 2026/27, being half of the £5,000. So £5,500 leaves his account on the same day. If he had budgeted only for the £3,000 he actually owed for last year, he is £2,500 short.

Which tax year you are filing for

This confuses almost everyone at first. On 31 January 2027 you are filing for the tax year that ran from 6 April 2025 to 5 April 2026, which is written as 2025/26. You are not filing for the year you are currently living in.

The reason for the gap is simply to give you time. The tax year ends on 5 April, and you then have nearly 10 months to gather everything and file. That generous window is why HMRC feels no sympathy at all about late returns, and why the penalties start the moment the deadline passes.

Who has to file a return

You must file if you were self employed with turnover above £1,000, if you were a partner in a partnership, or if you had untaxed income that HMRC cannot collect through your tax code. Untaxed income includes rent from property, dividends above the allowance, savings interest above the allowance, foreign income, and profits from selling assets.

You must also file if your income was over £150,000, if you or your partner claimed Child Benefit and one of you earned over £60,000, if you had capital gains to report, or if HMRC has simply sent you a notice to file. That last one matters. Once HMRC has issued a notice, the obligation exists whether or not you actually owe anything. If you believe the return is not needed you must ask HMRC to withdraw the notice, not just ignore it.

Company directors are a special case worth mentioning because the advice online is contradictory. There is no legal rule that every director must file. What there is, is a very high chance that a director has dividend income or a notice to file, either of which creates the obligation.

The registration deadline you may have already missed

If this is your first return, there is an earlier deadline. You must tell HMRC that you need to file by 5 October following the end of the tax year. Somebody who began working for themselves in August 2025 was in the 2025/26 tax year, so should have registered by 5 October 2026.

Registration matters because it generates your Unique Taxpayer Reference, and without a UTR you cannot file online at all. The reference arrives by post and can take a couple of weeks, sometimes longer in January when everybody else is doing the same thing. Leaving registration until the middle of January is one of the few ways to make the 31 January deadline genuinely impossible to meet.

The penalties, in the order they arrive

The penalty structure is fixed and automatic. It is not discretionary and nobody at HMRC decides to apply it.

The day after the deadline you get £100. This applies even if your tax bill is zero, and even if you are due a refund. It is purely for being late with the paperwork.

Three months late, on 1 May, daily penalties of £10 begin. They run for a maximum of 90 days, so they top out at £900. Combined with the initial £100 that is £1,000 before any tax has been considered.

Six months late, at the start of August, a further penalty of 5% of the tax due or £300 applies, whichever is greater. Twelve months late, the following February, the same charge applies again. On a modest bill you are now looking at £1,600 in filing penalties alone.

Late payment is charged separately

This is the part people most often get wrong. Filing late and paying late are two different offences with two different sets of penalties, and you can commit one without the other.

Late payment penalties are 5% of the tax still unpaid at 30 days, another 5% at 6 months and another 5% at 12 months. Interest also runs daily from 1 February until the day you pay, and it is charged on penalties as well as on the tax.

The practical lesson is important. If you cannot afford to pay, file anyway. Filing on time avoids the £100 and every filing penalty that follows it, and it gives you a known figure to negotiate with. Not filing because you cannot pay is the most expensive mistake in the whole system, and it is extremely common.

What to do if you have already missed it

File as soon as you possibly can, because the meter is running. Every additional day brings the daily penalties closer, and once they start they accrue whether or not you are in touch with HMRC.

Then look at whether you have a reasonable excuse. HMRC will cancel a penalty where something genuinely outside your control stopped you filing. Serious illness, a bereavement close to the deadline, a fire or flood, a prolonged failure of HMRC's own service, or a postal delay in receiving your activation code can all qualify. What does not qualify is finding the system too difficult, not receiving a reminder, relying on somebody else who let you down, or simply not having the money.

An appeal must normally be made within 30 days of the penalty notice, and you have to have filed the return before an appeal will be considered.

If you cannot pay the tax

HMRC offers Time to Pay, which spreads the bill over monthly instalments. For Self Assessment debts up to £30,000 you can often set this up yourself online without speaking to anybody, provided your returns are up to date and you are within 60 days of the payment deadline.

An arrangement generally stops further late payment penalties, though interest continues to run. The two conditions that matter are that you must have filed, and you must keep to the instalments. Missing a payment usually cancels the arrangement and brings the whole balance back into charge.

The other deadlines around the same date

31 January is also the last day to amend the previous year's return. So on 31 January 2027 you can still correct your 2024/25 return, which is useful if you have realised you missed an expense or a pension contribution.

It is also the deadline for paying any capital gains tax that was not covered by a 60 day property report, and for a partnership return where the partnership files online. And if you want tax you owe to be collected through your PAYE code across the following year rather than in one lump, you have to file by 30 December, a month earlier, and owe less than £3,000.

Working backwards from the deadline

The mistake is treating 31 January as the date you start. Treat it as the date everything must already be finished.

A sensible rhythm is to have your records complete by the end of September, the return drafted in October, and the figure for what you owe known by early November. That gives you nearly three months to find the money rather than three weeks. It also means that if something unexpected turns up, a missing statement or a question about whether an expense qualifies, there is time to resolve it properly rather than guessing.

If you use an accountant, ask what their internal cut off is. Most firms stop guaranteeing January filing somewhere in December, simply because of volume, and being told that on 20 January is not helpful.

Common mistakes that cost money

Forgetting payments on account is the biggest one, and it is covered in detail in a separate guide. After that comes forgetting income that HMRC already knows about, such as bank interest, dividends and rental income reported by letting agents. HMRC receives this information independently, so omitting it invites an enquiry.

Missing legitimate expenses is the quiet one. Use of home, mileage, professional subscriptions, training that maintains existing skills, bank charges on a business account and the cost of an accountant are all commonly left out. Pension contributions and Gift Aid donations are frequently missed by higher rate taxpayers, who are entitled to extra relief through the return and simply never claim it.

Finally, paying to the wrong reference. Your payment reference is your UTR followed by the letter K. Paying without it, or using an old reference, means the money sits unallocated while penalties accrue against a bill that technically remains unpaid.

A quick word on refunds

Plenty of people who file late are actually owed money back rather than owing anything. Employees who have overpaid through the wrong tax code, subcontractors who have had 20% deducted under the Construction Industry Scheme, and anyone who has stopped work part way through a year all commonly end up in credit. The frustrating part is that the £100 penalty still applies for filing late, so a refund of £600 can quietly become £500 for no reason other than delay. If you suspect you are owed money, that is a reason to file sooner rather than later, not a reason to relax about the date.

Refunds are normally paid within a couple of weeks of a straightforward return being processed, straight into the bank account you nominate on the return. If you have any tax debts outstanding elsewhere, HMRC will usually set the refund against those first rather than paying it out, so the amount you receive may be lower than the figure shown on your calculation.

Frequently asked questions