See for Caster Certificate or any other certificates, the organizers gives some deadline which clearly mentions that the certificate will be accounted valid if and only if it has been issued after the prescribed date. Now as per the NID 2022-23 official brochure there are no such prescribed date for the Caste certificate for SC/ST although its mentioned that the caste certificate must be issued in the english language only. For OBC NCL the case certificate must be issued between 01 April 2021 and 31 March 2022.

For the official brochure visit the link below:

https://admissions.nid.edu/NIDA2022/download/BDes_AdmissionsHandbook2022-23.pdf

For official website visit the link below:

https://admissions.nid.edu/NIDA2022/Default.aspx

To know more about NID visit the link below:

https://design.careers360.com/exams/nid-dat

I hope this answer helps. All the very best for your future endeavors!