Experts warn that taxpayers should always check their simple assessment for mistakes.
Simple assessment was originally introduced in 2017 to make the income tax process easier for people with simple tax affairs, including low-income retirees. About 560,000 calculations were issued for 2023-24, including 140,000 pensioners.
Antonia Stokes, of the Low Incomes Tax Reform Group, said: “While simple assessment can be a useful way to pay tax without the need to fill in a full self assessment tax return, the system is not perfect and taxpayers who receive one are advised to check that all sources of income are included.
“For example, bank interest information is usually received by HMRC directly from banks, but this data might not always be correct and complete.
“It is also important to remember that HMRC does not automatically receive data on dividends – where a taxpayer’s non-Isa dividend income exceeds the dividend allowance, it is down to the individual to contact HMRC and provide the necessary information.
“Finally, it is worthwhile checking that the simple assessment tax calculation is correct, and includes all necessary allowances and nil rate bands – such as the personal allowance, savings allowance, starting rate for savings and the dividend allowance.”
Taxpayers who think their simple assessment calculation is incorrect should contact HMRC within 60 days.
An HMRC spokesman said: “We have thorough processes in place to ensure customers fully benefit from any allowances or nil-rate bands they’re entitled to, provided we’re given the right information.”
