At four in the afternoon on Saturday, 31 January 2026, HM Revenue and Customs closed its Self Assessment phone lines. They are normally shut at weekends. This time HMRC had opened them at nine that morning and stretched its webchat to ten times its usual Saturday capacity, because it was the last day to file a 2024 to 2025 tax return online without an automatic £100 fine.
The busiest hour of the day came after the phones went quiet. Between 5 and 6 pm, 32,982 people submitted their returns. Between 11 pm and midnight, another 27,456 did. By the end of the day, 475,722 people had filed, and HMRC advisers had handled 10,483 calls and 5,409 webchats.
The window had been open a long time. A British tax year ends on 5 April, and an online return can go in from the next day. The deadline is 11:59 pm the following 31 January, almost ten months later. Self Assessment is for people whose tax isn’t all taken automatically from their pay, such as the self-employed and those with more than one source of income. More than 12 million were expected to file this round.
On 5 January, HMRC put out a progress report. More than 6.36 million had filed. Almost 5.65 million had not, with less than a month to go. The same release counted the people who had filed over New Year: 34,264 on New Year’s Eve, 342 of them in the last hour of 2025. Myrtle Lloyd, HMRC’s Chief Customer Officer, had a line for everyone else: “If you have yet to start, the clock is ticking, go to GOV.UK and start today.”
The last-day crowd is not new, and HMRC has published its size in early February for years. In 2023, 861,085 people filed on 31 January, 36,767 of them in the final hour. In 2014, 21,027 filed between 11 pm and midnight.
These figures need one caution. They record the moment someone pressed submit, not the moment they began. HMRC’s January release reminded people that a return can be started, saved and reopened as many times as needed before it is sent. Some returns are filed by accountants and other agents on their clients’ behalf, and Lloyd’s thanks after the deadline went to “the millions of people and agents” who made it. A return sent at 11:40 pm may be the end of weeks of work, or the last file in an accountant’s pile. The numbers show when people finish, not when they start.
What they do show is where the finish lands. Nearly half of the people expected to file had still not done so with less than four weeks left of a window almost ten months long.
About 1 million never made it. That was HMRC’s estimate of how many missed the deadline, each facing an initial £100 penalty that applies even when no tax is owed.
The next window opened on 6 April 2026. It closes at 11:59 pm on 31 January 2027.