Dear Manjula,
When one employee is covered under ESIC, and whenever, he fell sick, the concerned dispensary issues him a certificate allowing him to take rest depending on the sickness. One certificate is to be handed over at his office for their information and another copy of the certificate is to be submitted to the concerned local office. After completion of his sick leave, the concerned Medical Officer will give him a fitness certificate he will get monetary benefit from the ESIC local office and for the sick period, the office HR people will mark him as under ESI Leave. Hence he is not eligible for the sick leave. This is for your kin information.