Martin Lewis has told Britons to check old payslips within days or they risk losing out on money that could be owed.
The money saving expert reminded taxpayers that they only have until 5 April to check if their tax code was wrong for the year 2018/19, ahead of the new financial year beginning on 6 April.
If your tax code is wrong, then you could have been overpaying and therefore due hundreds of pounds back from HMRC.
Overpayments can only be backdated for up to four years, so taxpayers will no longer be able to claim their money back for 2018/19 come 6 April, but will still be able to claim their money back for later years.
Mr Lewis also warned in his newsletter that it is your - and not your employer’s - responsibility to check if your tax code is wrong, and that taxpayers should also check if they are underpaying.
The most common tax code that most working people will be on is 1257L (those earning between £12,501 and £50,000), and your tax code will be listed on your payslip.
You can also use the government’s online tax checker tool to view your tax code.
Mr Lewis’ website, Money Saving Expert, also has its own tax checking tool.
Your tax code is made up of three or four digits which can be multiplied by ten to see what you can earn tax-free a year.
If you are due a tax rebate HMRC will let you know by sending you a letter called a P800 or a simple assessment letter after the tax year has ended.
