The first step you have to take is you have to file a report in the nearest police station stating that in a theft you have lost your certificate. Then you have to get a certificate from that police station that you have filed a case, they have conducted an enquiry but could not trace out the certificate. Once you get that certificate, you have to approach the Institute where you have studied the course and give a written request for a duplicate copy and you have to attach the certificate given by police. You have to attach 3 passport size latest photographs and a copy of your school leaving certificate issued by the school. If you have a xerox copy of the original certificate you can attach that also. The school will advise you regarding the copies of certificates that are to be attached to your application. Then they will forward it to the board. The board may take about a month to send the duplicate copy to the school. Once the duplicate is received by the school, they will inform you. Then you have to go to the school and collect that. The fees required will change from state to state. The school will inform if any fee is required.