Hey!

Your class 12 private passing certificate will be provided to you later by the CBSE itself. If it is required in the college admission process then you will have to ask your school prinicipal to provide you with the certificate.

Thanks. All the best! 

Hi Ayaz
I suppose that you're asking when will be this certificate provided to you?
It will be provided later to you by the CBSE itself. But  If it is required in your Admission process in colleges just ask your school to make temporary or written certificate by the principal of your school.