Hi, 

The documents required for NIT counselling are:

Allotment letter

Jee score card

Jee admit card

Three passport size photograph

Candidate undertaking

Category certificate(if applicable)

Proof of fee for seat acceptance

Class 10th marksheet

Class 12th marksheet

Identity proof

Choice filling copy

Medical certificate. 

Medical certificate can be provided at a primary health care centre or by your physician. It shows that you are physically and mentally fit. It needs to be signed by a doctor who has min done his mbbs and has been provided by a registration number by the MCI. 

All the best