Martin Lewis has given an urgent warning to 1.8million people, as they could face a fine from HMRC.
The Money Saving Expert issued the alert in his weekly MSE newsletter.
The financial expert, who has his own ITV1 show the Martin Lewis Money Show, has warned people they face financial penalties for missing the HMRC tax deadline, reports Birmingham Live.
Martin said in the newsletter: "HMRC is waiving £100 fines for people who file returns after the January 31 deadline but by the Feb 28 cut-off.
"But 2.6% interest is still charged on outstanding tax from February 1.
"So many should consider paying an estimate ASAP even if they haven't done their return, and fail to do it before March 3 there's a 5% fee on top."
More than 10.7 million people submitted their 2019/20 self-assessment tax returns by the deadline.
Karl Khan, HMRC's interim director general for customer services, said: "Thank you to the 10.7 million customers who have sent in their tax returns.
"We won't send anyone a late filing penalty if they complete their tax return by February 28.
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"We know that many individuals and small businesses are finding it harder to pay this year, due to the pandemic.
"Anyone who can't afford to pay their tax bill in full can set up a payment plan, once they've filed their return, to spread their tax bill into monthly instalments."
