Still filing on paper? Your Self Assessment return must reach HMRC by 31 October

Illustration only. Published .

Maureen, an illustrative retired teacher in Norwich, has a routine she’s kept for years. Some time in October she gets out the paper SA100 form, a pen and a folder of statements, and works through her pension income and the rent from a small flat she lets out. Then she posts it to HMRC.

This year the routine has a hard edge. For the 2025 to 2026 tax year, HMRC must receive a paper return by 11:59pm on 31 October 2026. Posting it on the 30th and hoping isn’t the same thing. If it arrives late, there’s a penalty.

Why paper and online have different deadlines

There are two Self Assessment filing deadlines, and paper comes first.

  • Paper returns must reach HMRC by 11:59pm on 31 October 2026.
  • Online returns must be submitted by 11:59pm on 31 January 2027.

Whichever way you file, the tax you owe has to be paid by 11:59pm on 31 January 2027. So switching to online doesn’t give you longer to pay. It gives you three more months to finish the return.

You can file online through HMRC’s own service if you’re self-employed or have other income such as rent. You’ll need your Unique Taxpayer Reference, sign-in details you can create when you start, and you may be asked to prove your identity, usually with photo ID like a passport or driving licence. You don’t have to finish it in one sitting, because you can save it and come back.

GOV.UK lists some people who can’t use HMRC’s online service, including partnerships, trusts and estates, and people who lived abroad as non-residents. They use commercial software or paper forms instead.

The tax code option, and the date that matters for it

For people like Maureen, who already pay tax through PAYE on a pension or a job, there’s a quieter way to pay. If you owe less than £3,000, HMRC can collect the bill through your tax code, taking it in equal instalments over 12 months alongside your usual tax.

To get that, your return has to arrive in time. GOV.UK says that means a paper return by 31 October, or an online return by 30 December 2026. Miss those dates and you’ll have to pay another way, by 31 January.

If you qualify, HMRC sets this up automatically, unless you asked them not to on your return. There are limits. You can’t make a part payment to get under £3,000. HMRC also won’t collect it this way if you don’t have enough PAYE income for them to collect it, if you’d pay more than 50% of your PAYE income in tax, or if you’d end up paying more than twice as much tax as you normally do.

As an illustration only, if Maureen owed £1,200 and qualified, HMRC would collect it in 12 equal instalments of £100, rather than her paying £1,200 in one go in January.

What a late return costs

GOV.UK sets out the late filing penalties:

  • an initial £100 penalty
  • after 3 months, £10 a day, up to a maximum of £900
  • after 6 months, a further 5% of the tax due or £300, whichever is greater
  • after 12 months, another 5% or £300, whichever is greater

Paying late is a separate problem. There are penalties of 5% of the unpaid tax at 30 days, 6 months and 12 months, plus interest on the amount owed. If you have a reasonable excuse, you can appeal.

If you’ve only just registered

If you registered for Self Assessment after 5 October 2026, your filing deadline is different. HMRC will send you a letter or email giving you 3 months from its date to send your return. But the tax is still due by 31 January 2027, and GOV.UK warns that registering late and not paying in full by then may bring a “failure to notify” penalty.

Don’t forget July

If you make payments on account, there’s a second payment date to plan for. Payments on account are advance payments towards your next bill, each usually half of last year’s tax, due by 31 January and 31 July. You don’t have to make them if last year’s bill was under £1,000, or if more than 80% of your tax was already collected another way, such as through your tax code.

The first year you make them can sting, because January’s bill includes both the full amount for the year just gone and the first payment on account for the next.

Which way to go

If you’ve always filed on paper and your return is nearly done, the simplest thing is to get it in the post with time to spare. HMRC has to receive it by 31 October, not just have it sent by then.

If it isn’t nearly done, filing online moves your deadline to 31 January, or 30 December if you want to pay through your tax code.

Either way, it helps to know roughly what you’ll owe before January. Our Budget Planner can show how much you can set aside each month between now and then, and our Emergency Fund tool can help you build a separate pot so the bill doesn’t land on your everyday money.

Sole traders and landlords who had to join Making Tax Digital in April still file their 2025/26 return the usual way, and they have a quarterly update due on 7 November. We explain what it covers in our Making Tax Digital guide.

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Sources

All checked 22 October 2026.

Disclaimer

Maureen is an illustrative example, not a real person, and the £1,200 figure is illustration only. This article is general information, not financial or tax advice, and Money Engine is not regulated by the FCA. Check your own position on GOV.UK, with HMRC or with an accountant.