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Taxation (UK) · The systems for self-assessment and the making of returns

Self-Assessment Tax Returns and Filing Deadlines

Updated 11 October 2026 · Fact-checked

Self-assessment is how individuals report income and gains not fully taxed at source. You file if HMRC sends a notice to file, or if you are chargeable and must notify HMRC by 5 October after the tax year. Paper returns are due 31 October, online returns 31 January, unless the notice came late.

Understand Self-Assessment Tax Returns and Filing Deadlines

The UK tax year runs from 6 April to 5 April. Many people never file a return because all their tax is collected through PAYE. Others have income or gains that PAYE does not cover, such as profits from self-employment, rent, or a taxable gain. These people report to HMRC through a self-assessment tax return and work out their own tax.

You file a return if HMRC issues you a notice to file. If you have not received one but you are chargeable to income tax or capital gains tax for the year, you must tell HMRC. This is called notifying chargeability. You must do it by 5 October following the end of the tax year. For 2025–26, the tax year ends on 5 April 2026, so the deadline is 5 October 2026. There is generally no need to notify if all your income is taxed at source and you owe nothing further.

Once HMRC knows about you, it sends a notice to file. The return has two possible deadlines. A paper return is due by 31 October following the end of the tax year. An online return is due by 31 January following the end of the tax year. For 2025–26 these are 31 October 2026 and 31 January 2027. Most people file online because it gives three extra months.

Sometimes HMRC issues the notice late, after 31 July. The normal dates then do not give you enough time. A paper return is due three months after the notice is issued. An online return is due on the later of 31 January and three months after the notice is issued.

Filing is only half the job. The balancing payment for the year is normally also due on 31 January after the tax year. Late filing and late payment are penalised, but the details are in separate topics. In this topic, focus on who files, what the dates are, and how a late notice changes them.

Key rules to remember

Tax year
6 April to 5 April
Tax year 2025–26 runs from 6 April 2025 to 5 April 2026.
Notify chargeability
By 5 October following the end of the tax year
Applies if you are chargeable to tax and have not received a notice to file. For 2025–26, the date is 5 October 2026.
Paper return deadline
31 October following the end of the tax year
For 2025–26, this is 31 October 2026.
Online return deadline
31 January following the end of the tax year
For 2025–26, this is 31 January 2027.
Late notice to file: paper
Three months after the notice is issued
Applies when the notice is issued after 31 July, so the normal 31 October date would give less than three months.
Late notice to file: online
Later of 31 January and three months after the notice is issued
Never earlier than the normal online deadline.

How to solve Self-Assessment Tax Returns and Filing Deadlines questions

Use this method for any question on who must file and by when.

  1. 1Identify the tax year. Work out the 5 April on which it ends, for example 5 April 2026 for 2025–26.
  2. 2Decide whether the person is chargeable to tax for that year on income or gains not fully taxed at source, and whether HMRC has issued a notice to file.
  3. 3If there is no notice and the person is chargeable, set the notification date as 5 October after the tax year end.
  4. 4If a notice was issued, note its date. If it was issued on or before 31 July after the tax year, use the normal dates.
  5. 5State the paper deadline (31 October) and the online deadline (31 January) for the normal case.
  6. 6If the notice was issued late, add three months to the notice date. Paper uses that date. Online uses the later of that date and 31 January.
  7. 7Write the actual calendar dates with years, and state which method of filing each date applies to.

Quickest way: Date ladder from the tax year end

When to use it: Use this in objective test questions that ask for a single date.

  1. Write the year the tax year ends, for example 2026 for 2025–26.
  2. Read off: 5 October 2026 to notify, 31 October 2026 paper, 31 January 2027 online.
  3. Check the question for a late notice. If the notice date is after 31 July 2026, add three months.
  4. For online filing, compare your new date with 31 January and pick the later one.
  5. Check the filing method stated in the question before choosing between the dates.

Common mistakes in Self-Assessment Tax Returns and Filing Deadlines

  • Using 31 January 2026 as the online deadline for tax year 2025–26.

    Students link the deadline to the start year of the tax year instead of the year in which the tax year ends.

    Fix: The deadlines fall after the tax year ends. For 2025–26, the online deadline is 31 January 2027.

  • Confusing the 5 October notification date with a filing deadline.

    Both dates are in autumn and both relate to HMRC.

    Fix: 5 October is only the date to tell HMRC you are chargeable. It does not mean you file your return then.

  • Giving 31 October as the deadline for every return.

    Students remember the paper date and forget that most returns are filed online.

    Fix: Check the filing method. Paper is 31 October. Online is 31 January.

  • Applying the late-notice rule to a notice issued on time.

    Students memorise three months without the condition.

    Fix: The extra time only matters if the notice is issued late, after 31 July. Otherwise the normal dates apply.

  • Giving the late-notice online deadline as exactly three months after the notice, even when that is before 31 January.

    Students forget that the online date is the later of two dates.

    Fix: Always compare the three-months date with 31 January and take the later one.

  • Saying that someone with only PAYE income must always notify HMRC.

    Students assume any taxpayer must file a return.

    Fix: Notification applies when you are chargeable to tax and have not received a notice. If all income is taxed at source and no further tax is due, there is generally no need.

Worked examples

Example 1

Priya started self-employment on 1 July 2025. She has not received a notice to file. State when she must notify HMRC that she is chargeable to tax, and give her paper and online filing deadlines for 2025–26.

Show the solution
  1. Her self-employment profits are not taxed at source, so she is chargeable for 2025–26.
  2. The tax year ends on 5 April 2026.
  3. She has no notice to file, so she must notify HMRC by 5 October 2026.
  4. Once a notice is issued in the normal way, the paper deadline is 31 October 2026.
  5. The online deadline is 31 January 2027.

Answer: Notify by 5 October 2026. Paper return by 31 October 2026. Online return by 31 January 2027.

Example 2

HMRC issues Tom with a notice to file for 2025–26 on 20 November 2026. Give the latest date to file (a) a paper return and (b) an online return.

Show the solution
  1. The notice was issued after 31 July 2026, so the normal dates do not apply.
  2. Three months after 20 November 2026 is 20 February 2027.
  3. (a) The paper deadline is three months after the notice: 20 February 2027.
  4. (b) The online deadline is the later of 31 January 2027 and 20 February 2027.
  5. 20 February 2027 is later than 31 January 2027.

Answer: (a) Paper: 20 February 2027. (b) Online: 20 February 2027.

Exam tips

  • Always convert the tax year into actual calendar dates with years. Examiners use plausible wrong dates as distractors.
  • In objective tests, read the filing method. Paper and online answers are usually both offered as options.
  • If the question gives the date the notice was issued, check whether it is after 31 July before using the normal dates.
  • In written questions, set out the dates in a short list so they are easy to mark: notify, paper, online.
  • Do not spend time on penalty amounts here unless asked. Answer the date question first.

Practice questions from The systems for self-assessment and the making of returns

Self-Assessment Tax Returns and Filing Deadlines in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Self-Assessment Tax Returns and Filing Deadlines: frequently asked questions

Who needs to file a self-assessment tax return in the UK?

You file if HMRC sends you a notice to file. If you have not received one but are chargeable to income tax or capital gains tax on income or gains not taxed at source, you must notify HMRC by 5 October after the tax year.

What is the online filing deadline for a self-assessment return?

It is 31 January following the end of the tax year. For 2025–26 that is 31 January 2027. If HMRC issued the notice late, the deadline is the later of 31 January and three months after the notice.

What is the paper filing deadline?

It is 31 October following the end of the tax year. For 2025–26 that is 31 October 2026. A late notice gives three months from the date of the notice.

By when do I tell HMRC I am chargeable to tax?

You must notify HMRC by 5 October following the end of the tax year, if you have not received a notice to file. For 2025–26 that is 5 October 2026.