HMRC is slapping people with charges of up to £125 from Tuesday due to another key tax deadline.HM Revenue and Customs sets the self-assessment tax return deadline at January 31 every year.

This is the deadline by which any tax must be paid, and applies to anyone who has extra income they need to declare to the taxman, including those working self-employed, those with savings interest, income from side hustles, those who need to repay the Higher Income Child Benefit charge and various other reasons.

While HMRC will contact some people and ask them to register for self-assessment tax, it's ultimately your responsibility to know that you need to register and pay, and those who failed to register or failed to pay by January 31 now face another harsher deadline on Tuesday, March 3.

As of Tuesday, those still owing unpaid tax money to HMRC face a 5% penalty charge on the unpaid amount.

According to Robert Salter, a director at Blick Rothenburg, those who owed £2,000 in tax to HMRC but failed to pay until April 1 would face approximately £125 in extra charges from the 5% penalty.

He said: "The 5% surcharge means a taxpayer with a self-assessment liability of £2,000, settled on 1 April 2026 would face an additional cost of approximately £125 on top of the core tax due.

"This figure will continue to increase the longer the tax remains outstanding and additional 5% surcharges can arise where the tax is unpaid six and 12 months after the core payment deadline."

HMRC says in its guidance online: "If you send your tax return late

You'll get the following late filing penalties:

• an initial £100 penalty

• after 3 months, additional daily penalties of £10 per day, up to a maximum of £900

• after 6 months, a further penalty of 5% of the tax due or £300, whichever is greater

• after 12 months, another 5% or £300 charge, whichever is greater "

You'll get penalties of 5% of the tax unpaid at:

• 30 days

• 6 months

• 12 months