Hello David,

SC caste certificate is not sufficient for admission purpose because validity certificate is also the part of SC reservation certificate and without a validity certificate you cannot get admission with the benefit of SC quota in any of the institutions whether it is NSIT or any other.

Therefore I would recommend you to contact the concerned authorities of NSIT Delhi for the same, if they can provide you some time in which you can get your validity certificate.

I hope you got it.

Good Luck!!