When is a tax return treated as filed on time

A paper Self Assessment return is filed when HMRC receives it, not when you post it, and for most 2025 to 2026 returns it must arrive by 31 October 2026. An online return is filed only when HMRC’s system accepts it, which means completing the final submit step and getting confirmation; for 2025 to 2026 the online deadline is 31 January 2027. HMRC gives the benefit of the doubt for a paper return found in its letter box first thing the next working day, but not for one that arrives in the post on 1 November.

What are the filing deadlines?

Section 8(1D) of the Taxes Management Act 1970 requires a return for a tax year to be delivered by 31 October after the year ends if it is on paper and by 31 January if it is electronic. GOV.UK states the deadlines for 2025 to 2026 returns as 11:59pm on 31 October 2026 for paper and 11:59pm on 31 January 2027 online. Different dates apply where HMRC’s notice to file was given after 31 July, as explained in notice to file sent late.

Some returns cannot be filed online at all. GOV.UK and SAM120520 say trustees of registered pension schemes and non resident companies send paper returns, and those are on time if received by 31 January.

When is a paper return treated as received?

The statute uses the word “deliver”. HMRC’s Self Assessment Legal Framework manual at SALF203 says this is generally taken to mean that the return is received at an HMRC office on or before the relevant day. GOV.UK is blunt: HMRC must receive your paper return by the deadline, and you can send it any time from 6 April as long as it arrives in time.

SAM120520 explains how HMRC applies this around 31 October:

• Returns delivered before midnight on 31 October are on time.
• Returns delivered by hand and found in an HMRC office letter box when it is first opened on the first working day after 31 October are treated as delivered on 31 October for all purposes.
• Returns delivered by hand or received in the post on 1 November after the office has opened are late and attract a late filing penalty.

SAM120650 gives the reason: HMRC cannot tell whether a return found in the letter box on 1 November arrived before midnight, so it assumes it did, but there is no uncertainty about returns in that day’s post. It adds that the earlier practice based on Steeden v Carver no longer applies, because Schedule 55 to the Finance Act 2009 defines the penalty date as the day after the filing date.

There is one concession for postal delay. SALF203 says HMRC will normally accept a return as filed on time if it is clear the taxpayer took steps to ensure that, but it was delayed afterwards, for example by a Post Office delay. SAM121010 says HMRC does not acknowledge paper returns as a matter of course, so evidence of when and how a return was sent is your own responsibility.

When is an online return treated as filed?

Section 8(1H) lets HMRC prescribe what counts as an electronic return. Regulation 5 of the Income and Corporation Taxes (Electronic Communications) Regulations 2003 then says electronically delivered information is treated as delivered on the day the last of the required conditions is met, and is not delivered to an official computer system unless that system accepts it.

The Upper Tribunal decision in Perrin v HMRC [2018] UKUT 0156 (TCC) shows why this is important. Mrs Perrin went online on 2 January 2012, printed her return and received a reference number, but did not complete the final step of submission, so her return was not filed and she was charged late filing and daily penalties. HMRC’s letter in the case said a submission receipt was “not, in isolation, proof of submission”, and that a successful submission produces an onscreen message with a reference number and a confirmation email where an email address was given.

The tribunal recorded HMRC’s description of the current process. An unfinished return shows “not submitted” in bold. On the “submit your return” page you confirm the information is correct and complete by ticking a checkbox, and only then do you receive a notice that the return was successfully submitted with a submission receipt number. The return can still show as in progress until it passes HMRC’s validation.

In the same case Mrs Perrin later filed her information on the following year’s form. HMRC refused to accept it as the return for the earlier year. A submission is only a return for the year it is made for.

What if the return is rejected or incomplete?

A return that HMRC treats as unsatisfactory is sent back unlogged and does not count as filed (SAM120590). The replacement must reach HMRC by the filing date, although a paper filer whose return is sent back can switch to filing online by 31 January. The detail is in when a tax return is treated as incomplete.

If HMRC’s online service or your software fails near the deadline, that does not change the date the return was filed, but it can support a reasonable excuse appeal against the penalty provided you file without unreasonable delay once the problem is fixed.

Why does the exact filing date make a difference beyond penalties?

• The enquiry window. Under section 9A(2), if a return is delivered on or before the filing date HMRC can open an enquiry up to 12 months after the day it was delivered. If it is late, the window runs to the quarter day (31 January, 30 April, 31 July or 31 October) after the first anniversary of delivery. SAM120520 applies this to paper returns received on 1 November, giving HMRC until 31 January after the first anniversary.
• HMRC corrections. HMRC can correct obvious errors under section 9ZB within nine months of the day the return was delivered.
• Help with the tax. SAM120510 says HMRC will calculate the tax and tell paper filers what to pay by 31 January if the return is received by 31 October. GOV.UK says that to have a bill under £3,000 collected through your tax code you must file online by 30 December or on paper by 31 October.
• Your statement. GOV.UK says a return filed near the deadline may not produce a statement before payment is due, and online filers cannot view the calculation for up to 72 hours. See how to read your Self Assessment statement.

How does this work in practice?

Illustration only. Three people file 2025 to 2026 returns:

Person	What happened	Treated as filed	On time?
Anna	Hand delivered a paper return to an HMRC office letter box late on 31 October 2026; found when the box was first opened on Monday 2 November	31 October 2026	Yes
Ben	Posted a paper return second class on 30 October 2026; it arrived in HMRC’s post on 2 November	2 November 2026	No for paper, unless HMRC accepts he took steps to ensure it arrived in time
Cara	Completed her online return on 31 January 2027 at 11:30pm, saved it and logged off without pressing submit	Not filed	No; the return is still outstanding

Ben could have avoided the problem by filing online instead, because the 31 January online deadline had not passed.

What mistakes do people make about filing dates?

• Treating the postmark as the filing date. For paper returns, receipt is what counts.
• Stopping at a reference number. Check for the successful submission message and keep the submission receipt and confirmation email.
• Filing on the wrong year’s form. It will not count as the return for the year you meant.
• Assuming a filed return means a paid bill. The payment deadline is separate; see Self Assessment deadlines and penalties.
• Leaving amendments to the last minute. GOV.UK says you must wait 72 hours after filing online before updating a return; see amending a tax return.

If HMRC opens a check into your return, tax investigation insurance pays your accountant’s fees. Solar Protect cover pays up to £100,000 with no excess; it never pays tax, interest or penalties. Read how our cover works or get a quote.

Related Accountapedia entries

• When a tax return is treated as incomplete
• HMRC determinations when no return is filed
• VAT central assessments when no return is filed
• Benefits to participators treated as distributions
• Can HMRC send an information notice before you file

Sources

• legislation.gov.uk: Act 1970 c. 9, section 8
• GOV.UK: Deadlines
• GOV.UK: Manual page SAM120520
• GOV.UK: Manual page SAM120650
• GOV.UK: Manual page SALF203
• GOV.UK: Manual page SAM121010
• legislation.gov.uk: SI 2003/282, regulation 5
• GOV.UK: Christine perrin v the commissioners for hm revenue and customs 2018 u
• GOV.UK: Manual page SAM120590
• legislation.gov.uk: Act 2009 c. 10, schedule 55

Reviewed by Christine Anderson, Broker, Solar Protect. Last reviewed 24 October 2026. Part of Accountapedia, the Solar Protect guide to UK tax and accounting. This page is general information, not personalised advice.