Online tax returns must reach HMRC by midnight on 31 January.

Those who miss the deadline will be fined £100, regardless of whether they actually owe any tax.

From then on, the fine will be £10 per day for the next 90 days. Therefore, those who file three months late could face a £1,000 fine regardless of whether they owe tax or not.

The Association of Chartered Certified Accountants (ACCA) points out that many families will need to be conscious of the January deadline due to changes to child benefit claims.

Any parent who earns between £50,000 and £60,000 can elect to continue to receive child benefit but they must complete a self-assessment form and will have to repay a proportion of the benefit they receive, by way of a tax charge, at the end of the tax year.

Chas Roy-Chowdhury, ACCA head of taxation, says: “If you earn over £50,000 and continue to claim child benefit but do not complete a self-assessment form you could be liable, not only to repay part of all of the benefit claimed by way of a tax charge on the highest earner of the couple, but also interest and penalties on the tax unpaid, even if it is an innocent mistake. Parents filling in self-assessment forms on Christmas Day doesn’t sound very festive, but the fines for getting it in late or wrong can add up.”

More details about self-assessment, the deadline and penalties can be found on the HRMC website here.