Merchant Support Questions & Answers Is STAN unique? STAN is a 6-digit number that is unique only for 24 hours after purchase. Therefore, STAN + date (timestamp) is unique. Last Updated: 1 year ago in Questions & Answers Did this article answer your question? Related Articles Brand guidelines for MasterCard and VISA What is the difference between initial and standing amount? How to change email address on the payment page? What is Open Banking? What is processing account? What is EMV 3DS?