Around 700,000 people missed the 31 January deadline to file their tax return and pay their bill this year. These people will have automatically incurred a £100 penalty from HM Revenue & Customs.

After 30 days, they will have been fined another 5% of the tax due.

But on 1 May, a £10 a day fine kicks in for 90 days, until the bill is paid. If the return is not filed and tax due still isn’t paid, another fine of 5% of the outstanding tax is due.

“If you’re unable to pay a tax bill and are about to run up more fines, it’s always worth calling HMRC and explaining your position,” said Sarah Coles, personal finance analyst at Hargreaves Lansdown.

“They may set up a Time and Pay agreement, which lets you pay your tax over a fixed period of time, and avoid running up any more expensive fines in the interim. They’re more flexible over these if you call before you miss the deadline, but it’s worth asking.”

See YourMoney.com’s Top tips to get your tax return filed.