Hello Student..

The first stage in CBSE registration is for the school to register on the CBSE portal. Then, using the user id and password issued by CBSE for that student, they enter all of their pupils' information on the same portal. Each student is assigned a distinct registration number. This occurs in grades IX and XI. Your registration number can be found in the top right corner of the X marksheet.

For more information about this..refer to link below.

https://services.india.gov.in/service/detail/find-registration-number-cbse-school-affiliation

I hope this information helps.

Regards.