Lesson 3 · Practitioner · Both · 15 min
Authorization & ISO 8583 Concepts
Learn just enough ISO 8583 / auth messaging to debug declines, understand STAN/RRN, and talk to processors without drowning in bitmaps.
Objectives
- ▸Explain what an authorization message carries at a conceptual level
- ▸Recognize common fields: MTID, STAN, RRN, response codes, MCC
- ▸Distinguish auth, capture, reversal, and refund intents
- ▸Use response codes to drive UX and retry policy
Much of card switching still speaks ISO 8583 (or network-specific dialects derived from it), even when your gateway API is JSON. Understanding the conceptual fields helps decode processor logs, reconcile ARNs, and interpret mysterious declines.
Key terms
ISO 8583AuthorizationCaptureReversalSTANRRNApproval codeResponse codeMCCPartial auth