As of now, there is nothing announced for NEET 2018 so it is quite difficult like what all documents they can ask but to get a rough idea you can go through the documents which they had asked at the time of counseling of NEET 2017 below-

Admit Card/Hall Ticket of NEET 2017

Result of NEET 2017

Metric Certificate (for date of birth proof) Class XII certificate Passport size 10 photographs (same as affixed on application form) Identity prrof SC/ST proof certificate issued by the competent authority (if applicable) OBC certificate issued by the competent authority (if applicable) Physically Handicapped Certificate issued by the medical authority as mentioned in NEET 2017 prospectus (if applicable).

Hope this helps!!!