If you split an employee's payroll between categories, maybe you need to split payroll taxes as well.
If you have employees whose salary will be allocated to 2 or more different payroll accounts, e.g. Direct Wages, and Indirect Wages, you may need to allocate their payroll taxes to multiple accounts as well.
You can do this in the Variable type HR Formulas using the Multiple Target Category Type option.
This allows you to match a target category/account for the HR formula to each target category for the payroll, and will allocate the HR Formula result using the same percentage split as the payroll.
This may only be used for employees set up as Parent Employees.