Dear Sinuka, your post is too short, raising more questions in the reader's mind.
Resignation and Duty Attendance
After giving the letter of resignation, has the employee stopped coming for duty? How many days did the employee report for duty after submitting the resignation letter? Upon receipt of his resignation letter, did you issue him an "Acceptance of Resignation" letter? If yes, did you outline the procedure for handing over/taking over?
Handling Company Property
If the employee is in possession of the "Project code," you may issue a notice to him. The "Project code" is considered company property, and it was the employee's responsibility to return it. In the notice, clearly state that he is in possession of company property illegally and that if he fails to return it, a police complaint will be lodged against him.
Send this notice via "Speed Post with Acknowledgement Due." If the employee remains non-responsive, lodge a police complaint. If the employee approaches you to return the project code, instruct him to complete the knowledge transfer. Once the handover is complete, issue him a show-cause notice for the illegal possession of the project code. If the reply is unsatisfactory, proceed with a domestic inquiry. If misconduct is proven during the inquiry, take appropriate action against the employee, which may include termination of employment.
Ensuring Due Process
I recommend handling this matter with due sensitivity. Warning letters are typically issued for minor offenses, but this is a far more serious matter. Therefore, it warrants stringent action while ensuring due process of law is followed. Any loopholes could allow the employee to evade consequences. Stringent action will send a signal to all other employees regarding the consequences when an employee attempts to act cleverly.
Thanks,
Dinesh Divekar