Fake caste certificate is almost impossible to get. There are at least 10�15 documents that are required to be submitted such as Father's caste certificate, land records, Birth register extract, School records , Patwari report etc etc to get a caste certificate.
I have seen in many cases that many SC/ST/OBC people hide their true category in general social conversations to avoid the caste stigma. This creates a doubt in the minds of many regarding the true caste of a person.
Getting a caste certificate for even a geniune SC/ST/OBC person is such a difficult and time taking process,taking up to 60�100 days what to talk about a fake one.
But in case you really want to complain against someone, I would suggest you to be very sure and have adequate evidences against that person in the form of Land revenue records , Extract of Birth Register etc.
On of my friend had in a fit of mischief complained formally against one person whom he thought was faking his caste. The college authorities verified his certificate with the district authorities and it was found to be true. The person against whom my friend had complained found out about the complaint against him from college authorities. In turn now he has filed FIR against my friend in defamation ( 499 IPC ) , false complaint ( 182, 211 IPC) and some provisions of SC/ST Attrocities act also. Now my friend is in some trobule.
So my only suggestion to you is to be very sure about the case and only then proceed for such a action. It can also go against you as you can see.