An automated after tax deduction from an employees payslip can be setup using a Deduction Rule.
Example:
A deduction of $50 per week to recover payments for an employee training.
Navigate to Menu > Settings > Payroll Rules > Deduction Rules
Click the Create New Rule button to configure a new Deduction Rule.
Click the "Add New Rule" to confirm your new Deduction rule.
The Deduction Rule setup in the image above will automatically deduct $50 from the employee "James Adam" payslip titled as "Repayment Deduction".