There are just days left to file a self-assessment tax return to HMRC and avoid a £100 fine but those who have left it to the last minute are being thrown a lifeline.

Following a report by the Express that HMRC would not open its tax phone line on deadline day this Saturday, HMRC has now pulled a U-turn and announced that it will in fact now staff its helplines from 9am to 4pm on January 31.

Those liable to submit a tax return have until midnight on Saturday to file and pay what they owe, but at least those facing last minute problems will be able to speak to someone at HM Revenue and Customs to avoid potential problems with misfiling or errors.

Every January, HMRC sets its self-assessment deadline for those who need to submit a return to cover additional taxes they may owe. This is especially important for people who have received extra income on the side, rent a property, sold assets, are self-employed or who received Child Benefit and earn more than the threshold for repayment.

Those who fail to submit and pay their tax return by midnight on Saturday, January 31, 2026 face an automatic £100 fine, with extra interest charges on top for as long as the money remains unpaid. If you leave it for months without paying, you could rack up hundreds or even thousands in fines and unpaid tax interest charges. That’s because you will be charged 5% of the total tax owed after 30 days, six months and 12 months, which could be thousands.

HMRC has helplines open to assist people in filing their self-assessment tax returns, but these are usually only open on weekdays.

HMRC announced on Wednesday about its helpline: “HMRC webchat advisers will be available from 8am to 4pm on Saturday 31 January to deal with all Self Assessment queries.

“Our phone helpline will also be open from 9am to 4pm on Saturday 31 January to provide Self Assessment support.

“Our digital assistant is available 24 hours a day, seven days a week.”

To call HMRC before the deadline for help with filing, the number is 0300 200 3310.

Helen Thornley, Technical Officer for the Association of Taxation Technicians, said: “This is a sensible decision, allowing those who have not yet filed their tax returns to get any support they may need on the day.

“In 2025, almost 750,000 taxpayers filed their returns on the last day, while HMRC said last week that more than 3 million were yet to file their returns for 2024/25.

“Although there will now be additional support available on Saturday, anyone yet to file should take action sooner rather than later to avoid late filing penalties.”

According to HMRC, more than 3.3million people were yet to file their self-assessment with a week to go. 

It is urging taxpayers and agents who are yet to file to act now or risk missing the January 31 deadline and face an automatic £100 penalty.

Myrtle Lloyd, HMRC’s chief customer officer, said: “Don’t leave it until deadline day. Filing now will give you peace of mind that your tax return is completed and if you have tax to pay, you have a week to arrange payment.

“If you’re worried about paying your tax bill, you may be able to set up a payment plan online – search ‘difficulties paying HMRC’ on gov.uk.”