What is a UPI PIN? Updated February 21, 2019 20:41 Follow UPI PIN (UPI Personal Identification Number) is a 4 or 6 digit secret code used to authenticate UPI transactions. Related articles I forgot my UPI PIN, what to do now? How do I set the UPI PIN for my bank account from Truecaller Pay? How do I change my UPI PIN? What is a UPI ID? How do I set/reset my UPI PIN? Comments 0 comments Please sign in to leave a comment.