HMRC has said that it is in the process of reviewing individual cases to correct as many discrepancies as quickly as possible.
HMRC went on to add that, if an employee contacts an employer because they think their tax code may be wrong, then the employer should get them to call HMRC on the number printed on the coding notice or on 0845 3000 627.
The tax coding notices errors were first identified when HMRC issued 25 million notices earlier this year. There most common error is where people with one job have received two (or more) tax coding notices with different codes. This is because HMRC's new system, which combines information on NICs and PAYE details for the first time, has been failing to distinguish between current and previous jobs in all cases.
Without complete information on those taxpayers who have moved from one job to another recently, the new database has been treating them as if they are in more than one job.