
As long as One Administrator manages everything (like Payroll, Attendance, Employee profiles and Tasks management and everything else) related with its 20 employees then there is no need to make any payment, its FREE life long.
If you need that your employees also log in and take the benifits of Employee self service features like apply leaves, check approvals or send their daily status reports for assigned tasks and much more or if your employees are more than 20 than a paid plan is required.