First, delete the wage calculation. The payroll must be unfinalised before making any changes. Unfinalise the roll by clicking on the "Unfinalise Roll" button at the bottom right side of the screen.

To delete the wage calculation, select the employee by ticking the checkbox next to him, and delete it by clicking on the "Delete Selected Employees Calculation" button at the bottom right side of the screen.

Next, we need to remove the termination date. Go to the Employees screen from the HR tab, and select the employee.

Click on "Edit."

Scroll down to the Employment Details section and clear the Termination Date and Termination Reason fields.

Click on Save to save changes. Once done, re-calculate the payroll as per normal procedure.