hi,

In the official website of ssc there is format given for sc/st and other category certificates. however based on the Information, it is not mandatory to have central caste certificate, however candidates must issued the certificate from any of the  below list of certifying authority:

(i) District Magistrate/Additional District Magistrate/Collector/Deputy Commissioner/Additional Deputy Commissioner/Dy.Collector/Ist Class Stipendiary Magistrate/Sub-Divisional Magistrate/Extra-Assistant Commissioner/Taluka Magistrate/Executive Magistrate.

(ii) Chief Presidency Magistrate/Additional Chief Presidency Magistrate/Presidency Magistrate.

(iii) Revenue Officers not below the rank of Tehsildar.

(iv) Sub-Divisional Officers of the area where the candidate and/or his family normally resides.

follow the below link to know about the format:

https://ssc.nic.in/Downloads/portal/english/FORMAT%20FOR%20SCST%20CERTIFICATE.pdf