People who submit self-assessment tax forms after February 1 could face a £100 fine from HMRC.

Online tax returns must be submitted before the midnight 31 January 2025 deadline to avoid a £100 fee, which will increase if it’s submitted more than three months late.

Anyone doing a paper tax form has already missed the October 31, 2024 deadline by over a month and will need to pay a penalty, which can be avoided by submitting the form instead.

Any tax owed must also be paid by midnight on January 31, 2025, and further penalties will apply if the bill isn’t paid. However, there’s usually a second payment deadline of July 31 for making advance payments towards your bill.

If there is a “reasonable excuse” for submitting the form late, an appeal can be made against the penalty.

A self-assessment tax form must be submitted by anyone who fits HMRC criteria from the previous tax year, from April 6 to April 5.

This includes a partner in a business partnership, anyone with a total taxable income of more than £150,000, or anyone who had paid Capital Gains Tax when selling something that increased in value.

It also covers payees of the High Income Child Benefit Charge, and those who are self-employed as a ‘sole trader’ and earned more than £1,000 before tax relief.

Others may also need to send a tax return on any untaxed income, such as money from renting a property, tips and comission, income from savings and foreign income.

If you do not know what your profit will be for the whole tax year, the advice is to work out the likely sum and tell HMRC that the figures are provisional.