The standard deadline for UK taxpayers filing paper returns for 2025–26 Self Assessment is Oct. 31, 2026, while online filings and payments are due Jan. 31, 2027.
HM Revenue & Customs (HMRC) issued its reminder on Oct. 23, 2026, saying the online deadline was 100 days away. The agency estimates about 12 million people will file by Jan. 31, 2027.
The dates apply to different filing methods: the standard deadline for paper returns is Oct. 31, while the online cutoff also covers payment of any tax owed. The 2025–26 tax period includes income and gains from April 6, 2025, through April 5, 2026.
Self Assessment is the process HMRC uses to collect Income Tax that has not been routinely withheld from wages or pension payments. People and businesses with income outside those automatic deductions may need to report it on a return.
HMRC says filing before the deadline gives taxpayers more time to calculate their bill and plan for payment. People due refunds may also receive them sooner if they file early. Myrtle Lloyd, HMRC’s chief customer officer, said it was “the ideal time to get ahead and file your tax return early.”
Taxpayers who want a bill collected through their Pay As You Earn (PAYE) tax code must file online by Dec. 30, 2026. People new to Self Assessment need to register for a Unique Taxpayer Reference before filing.
HMRC’s 2026 tax return form sets an initial £100 penalty for a late return. The standard paper filing deadline is Oct. 31, 2026.
