Martin Lewis warns of urgent HMRC deadline as thousands risk missing tax refunds

Financial expert Martin Lewis has issued a critical warning to Britons, urging them to act on two separate but equally urgent deadlines from HM Revenue & Customs (HMRC) to avoid penalties and secure entitled payments.

The first, and most immediate, deadline is for families claiming Child Benefit. MSE has been urging parents to act by August 31 to avoid having their payments stopped.

The team's message on X told individuals to "act NOW," stating: "Child turned 16 and in full-time education or training? Act NOW to avoid losing Child Benefit! To keep getting your payments, contact HM Revenue & Customs by Sunday 31 August."

The specialist's website explains that Child Benefit is paid monthly to anyone responsible for a child under 16, or under 20 if they remain in full-time education or training. The rates for 2025/26 are £26.05 a week for the first child and £17.25 for each additional child.

Dame Meg Hillier said in a letter to HMRC: ‘I am alarmed that it was never deemed necessary to inform Parliament about an issue which affected such a vast number of taxpayers and led to the loss of £47 million of public money’ (picture posed by model/Dominic Lipinski/PA) (PA Archive)

The second critical deadline is for the Self Assessment tax return. While many people file online, the deadline for submitting a paper tax return for the 2024/25 tax year is October 31, 2025.

Anyone who misses this date faces an automatic £100 fine, even if no tax is owed.

This penalty can increase significantly over time. Those who miss the paper deadline can still file online until January 31, 2026.

According to HMRC rules, a tax return is required if you are self-employed and earn over £1,000, are a company director, or had a taxable income of £150,000 or more.

HMRC figures show corporation tax accounts for nearly half of Britain’s £46.8 billion tax gap (PA) (PA Wire)

The requirement also applies if you earned over £60,000 and claimed Child Benefit, or had significant income from rental properties, savings, investments, or foreign sources.

HMRC will never contact you by email or text message about a tax refund, so be wary of any such scams.

In order to ensure your return is processed smoothly and you claim all eligible tax reliefs, it is vital to avoid common mistakes like maths errors, not declaring all sources of income, and over-claiming expenses.

You can check your tax position and claim any refund owed via the HMRC app or your Personal Tax Account.