Hi aspirant,

A caste certificate once issued is vaild for many years. therefore the NC-OBC certificate issued in 2013 is valid even now and you can apply for CAT 2019 with this. The authority body says that a NC-OBC certificate is valid even if it is issued 3 years before but with a self declaration given by the candidate as per the format mentioned in the OM. therefore follow up the procedures.

hope this helps

all the best