What is a UPI PIN? Updated June 14, 2018 21:01 Follow UPI PIN (UPI Personal Identification Number) is a 4 or 6 digit secret code used to authenticate UPI transactions. Related articles How do I change my UPI PIN? Do I need to be a customer of a particular bank to use Truecaller? I forgot my UPI PIN, what to do now? 10 Cool Truecaller Tricks You Should Try! Watch Video Here! Truedialer, Truemessenger & Truecaller has stopped working? Comments 0 comments Please sign in to leave a comment.