Thousands of women could have been underpaid the state pension as far back as 1985, it has been reported.
Details of the lost cash has been uncovered in a new report which shows that one person was underpaid by a whopping £128,000.
In fact, an estimated 134,000 pensioners could be impacted with over £1billion owed between them.
The National Audit Office (NAO), which discovered the error at the Department for Work and Pensions, has reported the cause.
The report investigated the problems and published an insight into underpayments with retirees losing an average of £8,900.
Brits who claimed the state pension for the first time before April 2016 without a complete National Insurance record are affected.
According to the NAO, most people who are affected by the underpayments have been identified as women.
They should have received increases, but didn’t in an effort the NAO blamed on complex rules and outdated IT systems.
The DWP started to correct the mistake with some pensioners already receiving thousands of pounds.
According to the NAO, some pensioners who died in recent years may not receive what they owed.
An estimated 94,000 of the unpaid were still alive while another 40,000 died.
Head of the NAO, Gareth Davies said: “The impact of the underpayment of State Pension on those pensioners affected is significant.
“It is vital that the DWP corrects past underpayments and implements changes to prevent similar problems in future.”
The report says the exact amount and people affected isn’t certain, but the errors will be known once a review is completed.
According to DWP, it is working through identifying those affected and expects to have paid back the money by the end of 2023.
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A DWP spokesperson said: “We are fully committed to ensuring the historical errors that have been made by successive Governments are corrected, and as this report acknowledges, we’re dedicating significant resource to doing so.
“Anyone impacted will be contacted by us to ensure they receive all that they are owed.
“Since we became aware of this issue, we have introduced new quality control processes and improved training to help ensure this does not happen again.”
If money is owed, you must wait for the DWP letter to confirm your payment.