Hello Vikram,

You need not to worry much about missing your 12th exam registration number you can find it out in many ways one of them being you can contact the college which have studied your 12th standard and you can we get the registration number providing the details the management ask you like your name admission number or any other details like father name College ID etc.

Or you can go to indiaresults site and select the board which have studied your 12th class and enter your name along with your surname and the site will give you your registration number the best way to re get your registration number is any of those two ways but contacting your college would give you more success rate in re getting your registration number for class 12.