Dear Akarsh,
'Deputation' in employment is essentially a process involving the hiring out or exchange of an employee's services for a specified period between two employers through an agreement with the employee's consent. This arrangement involves two employers and one employee, namely, the original employer, the foreign employer, and the deputationist. The contract of employment between the original employer and the employee continues despite the deputation, maintaining basic employment features such as disciplinary control, sanction of increments, leave sanction, promotion, recall, etc. Thus, the original employer remains the de jure employer, while the foreign employer acts as the de facto employer concerning the day-to-day performance of the deputationist. The employee on deputation retains their right to employment, known as 'lien,' with the original employer as long as the deputation continues.
If you consider this legal position objectively while planning to exit during your deputation, it is advisable that your resignation be routed through the foreign employer to the original employer, who must accept it. Both employers should make the necessary relief arrangements. It is the responsibility of the original employer to issue the experience certificate.