Please note that now CBSE also sends us the Mark Sheet online digitally signed. We can get the same online at any time.
Anyway, I am giving hereunder the details to get the duplicate mark sheet:
Firstly, release a newspaper declaration for lost of mark sheet (documents)
You need to fill an application form (can be obtained easily from the website of CBSE) for duplicate mark sheet and attach the prescribed fee starting from INR 250 to INR 2000 (depending on the year of passing);
Up to 5 years from the year of passing INR 250
More than 5 years and 10 years from the year of passing INR 500
More than 10 years and up to 20 years of passing INR 1000
More than 20 years from the year of passing: 2000
All fees to be paid through crossed Indian Posted Order or Bank Demand Draft favoring "The Secretary, Central Board of Secondary Education" payable at the Regional Office.
Also, attach an identification certificate issued by the principal or gazetted officer, and some time they ask for the newspaper (press release).
The Regional Office of Delhi
Central Board of Secondary Education,
PS-1-2, Institutional Area, I. P. Extn.
There are other regional offices available at Chennai, Guwahati, Ajmer, Panchkula, Allahabad, Patna, Bhubaneswar.