Millions of taxpayers have been issued an urgent warning as they have mere weeks remaining to submit their online returns or risk facing substantial penalties. The cut-off date for filing your online tax return if you are self-employed is 31st January 2026.

According to the UK Labour Force Survey, whose data tax collector HMRC uses, there were 4.39 million self-employed people in the UK in the July to September period this year.

Missing this deadline could result in an immediate £100 fine if your tax return is submitted up to three months late. Beyond that point, you’ll incur additional daily penalties of £10 per day, capped at a maximum of £900.

The penalty structure works as follows: an initial £100 charge, followed by daily penalties of £10 after three months, reaching a ceiling of £900.

At the six-month mark, a further penalty of either 5% of the tax owed or £300 applies, whichever sum is higher.

After 12 months, another charge of 5% or £300 is levied, again whichever amount is greater. Payment must be made within 30 days of receiving the penalty notice.

Should you need to amend your tax return after submission – perhaps due to an error – you can do so.

Your bill will be recalculated based on the updated information, potentially resulting in additional tax owed or a refund due, reports Birmingham Live.

Corrections to a tax return can be made within 12 months of the Self Assessment deadline, either online or by submitting another paper return. Lucy Pike, HMRC’s chief security officer, cautioned: “Millions of people file a tax return each year and scammers mimic HMRC to try and catch unsuspecting victims out.

“I’m urging people to stay vigilant and if any emails, text messages or phone calls appear suspicious – don’t be lured into clicking on links or sharing your personal information – report it directly to HMRC.”

Brits may be required to file a self-assessment tax return if they receive Child Benefit payments and need to pay the High Income Child Benefit Charge due to either them or their partner earning more than £50,000.

The Labour Party suggests using the online tool on the GOV.UK website to determine if you need to file a tax return.