In some African countries, it is not common practice to calculate employees' tax using the periods worked on a pro rata basis for the periods worked, when an employee is engaged or terminated during a month.
For example, if an employee started working on 10 March, they would have only worked 22 days for the month. By system design, the prorated "Periods Worked" calculation will show 22 days worked out of 31 calendar days in March = 0.7096774194 (i.e. a fraction of the month worked). This figure will be used in the tax calculation (0.7096774194/12).
To change the calculation to use 1/12 for all employees, regardless of their engagement or termination date, you should enable the "Always round periods
up to accumulate one period worked when calculating periods worked" checkbox under the General Calculations section on the General Settings screen.
Navigate > Configuration > Payroll > Payroll Config > Calculation Settings > General Calculations
The employees' Tax Certificates / Historical Drill Down screen will show that the Periods Worked value has changed from 0.709677419 to 1.
Navigate > Employee > Payroll Results > Tax Certificates / Historical Drill Down
Before the company setting was enabled -
After the company setting was enabled -