National Insurance (NI) arrears may not calculate automatically when an employee's NI category changes during a payroll period. This happens because the system requires manual intervention to recalculate historical contributions when these category changes impact previous calculations.
The payroll system cannot determine the correct arrears amount automatically without specific updates to the employee data, as NI category changes can have complex, retrospective effects on contribution calculations and thresholds.
To resolve this, support will need to update the affected employee data. Please raise a new case online, referencing this article's title and include the following details:
Employee number
Pay group
Current payroll period
Period effective for the category.
Manual payment dates.