Dear candidate, not every class’s certificate is important for the future. However, class 10th and 12th certificates must be kept safely for future use. If your 10th and 12th certificate is lost then, follow these steps: (All boards maybe having different rules, but basic criteria is same)

• File an FIR in the nearest police station.
• Fill an application form, given on the council's website.
• Fill the application form carefully.
• An Affidavit on Non-Judicial Stamp Paper of Rs.10 should be filed.
• Prepare a demand draft for the requisite amount.
• Attach identification certificate of a gazetted officer or principal.
• Attach the new paper declaration/press release.
• Send it to the CBSE regional office with all attachments(Address is given on council’s website).

Hope, it helps!