UK Self Assessment Deadlines 2026: 31 October or 31 January 2027?

Oct 27

4 min read

As October progresses, many sole traders, landlords and people with additional income ask whether Self Assessment ends on 31 October.

For the 2025/26 tax year, the usual answer is: paper tax returns are due by 31 October 2026, while online returns are normally due by 31 January 2027. These deadlines should not be confused. HMRC publishes separate filing and payment dates.[1]

1. Start with the correct tax year

The UK 2025/26 tax year ran from 6 April 2025 to 5 April 2026. The return now being prepared concerns that completed year, not the 2026/27 tax year that began on 6 April 2026.[1]

Requirement：First notification that a 2025/26 return is required；Usual date：5 October 2026 — passed；Important point：If missed, register as soon as possible; a fixed penalty does not necessarily arise immediately
Requirement：Paper 2025/26 Self Assessment return；Usual date：31 October 2026；Important point：HMRC must receive it by the deadline; posting it on that date is not enough
Requirement：Online return where an eligible debt is to be collected through PAYE coding；Usual date：30 December 2026；Important point：Available only where HMRC's conditions are met
Requirement：Online 2025/26 Self Assessment return；Usual date：31 January 2027；Important point：The usual online filing deadline
Requirement：Payment of the 2025/26 balancing amount；Usual date：31 January 2027；Important point：Some taxpayers may also owe a payment on account for the following year

These are the standard dates in HMRC's Self Assessment guidance. A taxpayer who receives a late notice to file, or who falls within a special category, may be given a different filing deadline.[1]

2. Who may need to submit Self Assessment?

Common circumstances include:

Trading as a sole trader with gross trading income above £1,000 during the tax year.
Being a partner in a business partnership.
Receiving property income, overseas income, savings interest or dividends that need to be reported.
Having a Capital Gains Tax matter that must be reported through Self Assessment.
Owing the High Income Child Benefit Charge where it has not been dealt with through PAYE.[2]

Not every company director, landlord or employee above a particular salary automatically needs to submit a return. The requirement depends on the type and amount of income, any formal notice to file issued by HMRC and the applicable rules. Anyone uncertain should use HMRC's Check if you need a tax return service.[2][3]

3. What if the 5 October registration date was missed?

A person who needed to notify HMRC for the first time—or needed to reactivate a Self Assessment obligation for 2025/26—would normally have done so by 5 October 2026. Someone discovering the issue after that date should register promptly rather than wait until January.[1]

HMRC explains that registration after 5 October may lead to a filing date that differs from the usual annual deadline, potentially three months from the date of HMRC's notice or email. However, the 31 January 2027 tax-payment date is not automatically postponed. Unpaid tax after the applicable date can result in interest and penalties.[1][4]

It is therefore inaccurate to say either that late registration always produces an immediate £100 penalty or that all payment obligations automatically move back by three months.

4. Does missing the paper deadline mean a penalty is unavoidable?

Not usually. A person who can file online and is still within the applicable 31 January 2027 deadline may be able to switch to online filing. Sufficient time should be allowed to obtain or recover an HMRC account and UTR and to arrange any necessary software. Some taxpayers must use commercial software.[1][5]

If the final applicable filing deadline is missed, HMRC's current rules normally impose an initial £100 late-filing penalty. Additional penalties can arise after longer periods of delay. A late return penalty is separate from late-payment penalties and interest on unpaid tax.[4]

5. What records should be prepared?

The exact documents depend on the taxpayer's income sources, but commonly include:

P60, P45 where relevant, P11D and tax-code information for employment.
Business income, allowable-expense records and supporting documents for self-employment.
Rental income, property expenses, finance-cost information and property records for landlords.
Bank interest, dividends, overseas income and any foreign tax deducted.
Pension contributions, Gift Aid donations, tax already paid and the previous year's Self Assessment records.

Collecting the documents is only the first step. The taxpayer must determine which costs are deductible, which income has already been taxed through PAYE or another mechanism and whether any amount would otherwise be duplicated or omitted.

Frequently Asked Questions

Q: I have one ordinary PAYE job. Must I automatically file Self Assessment?

Not necessarily. Most employees do not file solely because they are employed, although other reportable income or a formal HMRC notice to file can change the position.[2]

Q: Is 31 October only the paper-return deadline?

Yes. For a usual individual 2025/26 return, online filing is generally due by 31 January 2027. The October date should not be described as the final deadline for everyone.[1]

Q: Once the return is submitted, can I wait for HMRC to remind me to pay?

That is not advisable. Filing and payment are separate legal obligations. Tax due for 2025/26 will normally need to be paid by 31 January 2027.[1]

The essential task is to distinguish the dates for notification, paper filing, online filing and tax payment. Taxpayers with self-employment, rental, overseas income or several different tax roles should start the review early enough to confirm both the reporting requirement and the applicable deadline.

This article provides general tax information based on HMRC guidance available by 21 October 2026. The dates are the usual rules for 2025/26 and do not constitute personal tax advice.

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