Hello Mitui,

As per the official guidelines of GATE authority mentioned in the brouchure, producing caste/category certificate is mandatory for availing the benefits of the same. So if in case you're not able to produce the certificate at the time of admission you will be considered in GEN or OPEN category and you'll not be able to avail the concession given to the students belonging to the same throughout the course you have taken admission for.

Hope it helps.