HMRC have raised awareness of when Category M should be used.
Category M no longer applies after an employee reaches the age of 21 and it’s the employee’s age at the time of payment that determines which National Insurance contributions category should be used. For example, if an employee turns 21 during a tax month but is not paid until later in the month then Category M should not be used for that month’s pay.
This reminder is based on insight that suggests employers aren’t changing the National Insurance contributions Category until the month after the employee turns 21.
HMRC urges employers to review their payroll systems and ensure that the correct date of birth is recorded, and any incorrect dates of birth are rectified. This will help reduce any payroll errors in future.