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Diagram showing the structure of an ISO 8583 message

ISO 8583

What Fields Make Up ISO 8583?

We covered the ISO 8583 basics in an earlier article. This post explains the ISO 8583 message structure in detail: every ISO 8583 message consists of three main parts - the MTI (Message Type Indicator), the Bitmap, and the Data Elements.

POS payment terminal illustration

Credit Card

What is Dual Messaging?

When the card-issuing bank and the POS bank are different, first obtaining authorization and then running the clearing process to finalize the transaction is called Dual Messaging. So why is a dual message structure needed?

Diagram showing how card transaction data flows through the ISO 8583 messaging standard

Merchant & POS

What is ISO 8583?

Introduction: When a card (credit card/debit card/prepaid card) is used at an ATM or POS, data must be carried securely between systems. For example, in a store sale, the POS initiates the transaction, which must reach the cardholder's bank intact.

Illustration representing communication protocols used in POS payment systems

Merchant & POS

What Are POS Sub-Protocols and Their Use Cases in Turkey?

In payment systems, every exchange between POS devices and bank or payment institution systems runs on a specific messaging standard, generally based on ISO 8583. However, each country, bank, or switch network defines its own version of this standard.

Illustration of dynamic CVM limit management for contactless card payments

Payment Systems

Dynamic CVM Limit Management Approach: A New Era in Card Security

One of the most notable recent developments in card payments is that contactless limits are no longer fixed and can be managed dynamically per customer. Mastercard and Visa are taking different but complementary approaches, and ISO 8583 may need to evolve with them.

Diagram of a partial authorization where an issuer approves only part of the requested amount

Merchant & POS

What Are the Partial Authorization Requirements for an Acquirer Bank?

Partial authorization lets an issuer approve part of the requested amount when the card lacks the full balance, with the rest paid another way. This post covers the technical, receipt, clearing, reconciliation, merchant and certification requirements for acquirers.

POS terminal used for processing card payments at a merchant

Merchant & POS

How Does a POS Device Communicate with the POS Bank?

A POS is a functional device with its own dedicated software, customized to the authorization system of the bank it is connected to, that accepts credit or debit cards. The POS and the authorization system communicate using the ISO 8583 standard.

ISO 8583 F124 field structure and subfield breakdown

ISO 8583

ISO 8583 Field Descriptions (F124)

F124 (Private Additional Data) contains additional information specific to the transaction, such as Card Update Failure Code and Status, cardholder name in money transfers, and keys in network management messages.

Diagram of the ISO 8583 field F45 Track 1 data structure

ISO 8583

ISO 8583 Field Descriptions (F45)

F45 (TRACK-1 DAT) carries the Track 1 data of the card in ISO 7813 format, including field separators and start and end sentinels but excluding the LRC character. It is 76 characters long.

Diagram explaining the Visa Purchase Return Authorization process for card refunds

Credit Card

What Is Purchase Return Authorization?

A structure developed by Visa for purchase refund transactions. The purchase return authorization message lets cardholders view their refund transactions in real time, improving the customer refund experience.