The 31 October Paper Self Assessment Deadline: Who Still Files on Paper and Why

The paper Self Assessment deadline is 31 October: for the 2025 to 2026 tax year, HMRC must receive a paper return by 11:59pm on 31 October 2026. It matters to people who cannot or do not file online, including non-residents without suitable software, some trustees and anyone who wants a small bill collected through their tax code. Everyone else has until 31 January 2027 to file online.

This guide is for UK taxpayers who are about to post a return, and for Americans in the UK and British nationals living abroad who have discovered that HMRC's online service will not take theirs. It explains who the 31 October date applies to, what it does and does not change, and the options if you are not going to make it.

When is the paper Self Assessment deadline, and what exactly is due on 31 October?

The return, and only the return. GOV.UK's Self Assessment deadlines page sets out the dates for the 2025 to 2026 tax year, which ran from 6 April 2025 to 5 April 2026:

What	Deadline for 2025 to 2026
Tell HMRC you need to file (register)	5 October 2026
Paper return received by HMRC	11:59pm on 31 October 2026
Online return, if you want the tax collected through your tax code	11:59pm on 30 December 2026
Online return	11:59pm on 31 January 2027
Pay the tax you owe	11:59pm on 31 January 2027
Second payment on account, if you make them	31 July

Two details in that wording are easy to miss. The paper deadline is the date HMRC must receive the return, so posting it on 31 October is too late. And the payment date does not move: a paper filer has the same 31 January 2027 payment deadline as an online filer.

There is one exception to the dates above. If you registered after 5 October 2026, GOV.UK says the letter or email from HMRC will give you a return deadline three months from the date on it.

Who still files a Self Assessment return on paper?

Four groups. Two choose paper and two are pushed towards it because HMRC's own online service does not cover them.

1. People who prefer paper

Paper remains a permitted way to file the main SA100 return. GOV.UK says you can download the main form or call HMRC and ask for it, and that all the supplementary pages can be downloaded. Some people have always filed this way, and some lack the access or confidence to file online. The cost of the choice is three months.

2. People who want the bill collected through their tax code

If you are employed or receive a company pension, HMRC can collect a Self Assessment bill through your PAYE code instead of asking for a lump sum. GOV.UK lists three conditions: you owe less than £3,000, you already pay tax through PAYE, and you filed a paper return by 31 October or an online return by 30 December. It will not be done if you do not have enough PAYE income, if it would mean paying more than 50% of your PAYE income in tax, or if you made a part payment to get under £3,000.

For this group the paper date is not a burden. It is one of two ways to qualify, and the online route gives two extra months.

3. Non-residents

This is the group most often caught out. GOV.UK states that you cannot use HMRC's online services to tell HMRC about your income if you are non-resident. It gives three alternatives: fill in a Self Assessment return and an SA109 form and send them by post, use commercial Self Assessment software that supports SA109 reporting, or get a tax professional to report your UK income for you.

The SA109 is the supplementary page for residence and remittance basis matters. A British national who has moved to the United States and still has UK rental income, or an American who left the UK part-way through the year and needs to claim split-year treatment, will normally need it. If such a person plans to complete the forms themselves without buying software, they are a paper filer and their deadline is 31 October. Our page for Brits in the US covers the wider position.

4. Trustees, personal representatives and a few special cases

For trusts and estates, GOV.UK says trustees can buy software to send the SA900 electronically by 31 January, or fill in the paper form and post it by 31 October. HMRC's own online service is not offered as a route.

GOV.UK also lists other returns for which commercial software is the online route: partnerships, people receiving income from a trust, Lloyd's underwriters, religious ministers and people reporting chargeable gains on more than one asset. Anyone in those categories who does not use software or an agent ends up on paper.

One group runs to a different timetable altogether. Trustees of a registered pension scheme and non-resident companies cannot file online, and GOV.UK gives their paper deadline as 31 January 2027.

Paper or online: what changes?

	Paper return	Online return (HMRC service or commercial software)
Filing deadline, 2025 to 2026	31 October 2026, received by HMRC	31 January 2027
Payment deadline	31 January 2027	31 January 2027
Tax code collection cut-off	31 October 2026	30 December 2026
Proof of filing	Your own proof of postage and delivery	Immediate submission receipt
Available to non-residents	Yes, with the SA109	Only through commercial software or an agent
If you miss it	File online instead by 31 January	Late filing penalties begin

What if you are going to miss 31 October?

Switch route. This is the most useful sentence in HMRC's guidance on paper returns: the SA100 page on GOV.UK, updated on 8 September 2026, says that if you miss the paper filing deadline you should send your tax return online instead to avoid a penalty.

In practice that leaves three positions.

1. You can use HMRC's online service. Register for it if you have not already, and file by 31 January 2027. Do not post a late paper return as well.
2. You cannot use HMRC's service but can use commercial software. This is the usual answer for non-residents and for returns that include the SA109. Buy software that supports the pages you need, or instruct an adviser who has it. The deadline becomes 31 January 2027.
3. You must file on paper. Get the return to HMRC as soon as you can. A late paper return is still a filed return, and penalties grow with time.

If a paper return does arrive late and you have not filed online, the late filing penalties on GOV.UK are an initial £100, then after three months £10 a day up to a maximum of £900, then after six months a further 5% of the tax due or £300 if greater, and after twelve months another 5% or £300. Late payment brings separate penalties of 5% of the unpaid tax at 30 days, six months and twelve months, plus interest. You can appeal if you have a reasonable excuse. Our guide to the late Self Assessment penalty works through the figures.

How to send a paper return that arrives on time

1. Use the right year's forms. Download the SA100 for the tax year ended 5 April 2026 and each supplementary page you need. Our SA100 guide lists the pages cross-border filers use, including the SA106 for foreign income.
2. Sign and date the declaration. Check every page is included before you seal the envelope.
3. Post it to the correct address. GOV.UK gives Self Assessment, HM Revenue and Customs, BX9 1AS for UK residents, and HM Revenue and Customs, Benton Park View, Newcastle Upon Tyne, NE98 1ZZ, United Kingdom for returns sent from outside the UK.
4. Allow for the post. The test is receipt by 11:59pm on 31 October 2026. From the United States, a week is not a safe margin.
5. Keep proof. Use a tracked or signed-for service and keep the receipt with a full copy of what you sent.
6. Diarise the payment. Filing in October does not pay the bill. The tax is due by 31 January 2027.

Illustrative example: a British software engineer moved to Seattle in 2024 and lets out his flat in Leeds. In mid-October 2026 he logs in to HMRC's online service to file his 2025 to 2026 return and finds no way to add the residence pages. He downloads the SA100, SA105 and SA109, but airmail to Newcastle will not reliably arrive by 31 October. He stops, buys commercial software that supports the SA109 and files online in November, well inside the 31 January 2027 deadline. Had he posted the paper return and it arrived on 4 November, the £100 penalty would have applied. This example is illustrative and does not describe a real client.

Where the US return fits

For Americans in the UK, late October is crowded. A US return on extension is due on 15 October, and the UK paper date follows sixteen days later. The two returns feed each other: the UK tax on your Self Assessment return is what supports the foreign tax credit on the US one. If your UK return has to be filed on paper, that is a reason to prepare it first, not last.

For most Americans resident in the UK there is no need to file on paper at all, because UK residents can use HMRC's online service or software. The people who need to watch 31 October are those who left the UK during the year, or who live in the US with UK income. If you are deciding whether to do this yourself, our article on expat tax software versus specialists explains where each country's software stops.

What people get wrong about the 31 October deadline

"It is the date to post by." It is the date HMRC must have the return.

"If I file early on paper, I pay early." The payment date is 31 January 2027 either way.

"I missed 31 October, so I am already late." Not if you can file online or through software by 31 January.

"I live abroad, so I will just use the HMRC website." HMRC's online service is not available to non-residents. Plan for software, an adviser or paper.

"I registered late, so I have missed everything." If you registered after 5 October, check the letter or email from HMRC for a three-month filing deadline. If you have not registered yet, see our guide to registering for Self Assessment.

Getting it filed

If you are a paper filer by choice, post early and keep proof. If you are a paper filer by accident, because HMRC's service will not accept your return, the better answer is usually to file electronically through software or an adviser and use the January date.

US/UK Cross Border Tax — US CPAs and UK tax advisers working as one team; London, Manchester, New York, San Francisco. Our UK Self Assessment service files returns with the SA106 and SA109 electronically, which puts you on the Self Assessment deadline 2027 of 31 January instead of 31 October 2026. To check which deadline applies to you, get in touch.