31 January 2027: Online Self Assessment return and payment
By midnight on 31 January 2027: file the 2025/26 return online, pay any tax owed for 2025/26, and pay the first payment on account for 2026/27.
Is this you?
Everyone in Self Assessment: sole traders, partners, landlords, company directors with dividends or other untaxed income, higher earners with child benefit or pension charges to report.
The detail
Three things fall on the same day. The return itself. The balancing payment: the tax for 2025/26 less anything already paid on account. And the first payment on account for 2026/27, usually half of the 2025/26 bill, if that bill was over £1,000 and mostly not collected at source.
The tax figure only exists once the return is done, so the practical deadline for handing your accountant the records is much earlier. Buzz asks for them in the autumn and files early, so you know the number months before it is due.
What it costs
Late filing: £100 immediately, even if there is no tax to pay. After three months, £10 a day for up to 90 days. After six months, a further 5% of the tax due or £300, whichever is more, and the same again at twelve months.
Late payment: 5% of the unpaid tax at 30 days, another 5% at six months and another at twelve months, plus interest from the due date. Source: gov.uk and Companies House guidance, checked September 2026.
Now
Get the records to your accountant early. If you cannot pay in full, HMRC offers Time to Pay arrangements, set up online for smaller bills; the return must still be filed on time.
