Martin Lewis has given millions of Brits a 20-day warning before they face £100 fines.

The Money Saving Expert issued the warning on ITV’s The Martin Lewis Money Show, which returned to screens on Tuesday.

Discussing the deadline for filling out the tax self-assessment form, Mr Lewis warned that Brits could be fined £100 if they missed the January 31 deadline.

Mr Lewis urged people not to leave it to the last minute, due to the risk your form could be clogged in the HMRC backlog.

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The warning affects people who are self-employed with income of more than £1,000 or if HMRC have said you underpaid on tax last year.

It also includes people who are high earners, earned income from abroad, or earned money on savings and investments.

You could receive a £100 late filing penalty if your tax return is up to three months late, even if you don’t have any tax to pay.

You will then receive a further £10 fine for each day it is late over three months, up to £900.

Mr Lewis said: "If you have been sent one, even if you don't think you should have, you have to fill it in and ask them not to send you once again next year.

“Do not leave these to the last minute. There are reports from MPs that the HMRC helpline is clogged and taking a long time to answer.

“The later you leave it, the more at risk you won't be able to get your questions answered and the more you're going to miss that deadline."