Hii neeraj!

You can check CBSE class 12th registration number in:

• Your class 12th board exam admit card. Please do check admit card for registration number, it must be there.
• You can also check the registration number in your class 12th marksheet in case you have got it.
• Alternatively you can also visit your school and ask for the same in the administration office they may tell you the registration number.

Hope it helps!