The deadline depends on how you file. If you file your Self Assessment tax return online, the deadline is 31 January following the end of the tax year. So for the 2025/26 tax year (which will end on 5 April 2026), the online deadline is 31 January 2027. If you file a paper return, the deadline is earlier — 31 October following the end of the tax year. It is worth noting that even if you file your return by the January deadline, HMRC needs it by 30 December if you want any tax owed to be collected through your PAYE tax code rather than paid as a lump sum. Filing early is always a sensible approach.
