Hi,
We have a similar system at our company, but in this case, you need to clearly state that the employee is appointed purely on the basis of contractual terms, and the said contract will expire on completion of the mentioned term period. Alternatively, you can hire an employee as a consultant/freelancer for special services. In this scenario, you would need to ask the employee to prepare a bill of his work for the month, sign it, and make payments based on that. This is the safest way.
However, as an HR professional with ethics and principles, I do not agree with such systems, as I have already communicated to my management (even if they did not agree). These systems tend to take advantage of employees or deceive them. The second approach mentioned above is acceptable when the person is retired and looking to save on taxes, and I support that.
Regards,
Meghal