ISO 8583
The foundational financial transaction message standard used by ATMs, POS terminals, card switches, and payment gateways worldwide. Every card payment you make passes through this protocol.
Message Type Reference
ISO 8583 messages travel in request/response pairs. The request originates at the acquirer; the response comes from the issuer (via the network). Advice messages do not wait for a response before proceeding — they are sent to inform, not to ask permission.
Message flow — authorization & reversal
A request/response pair travels from the terminal to the issuer and back. The MTI changes from request (x100/x200) to response (x110/x210) on the return path.
0100 / 0200 Request
Terminal sends an authorization request to the acquirer.
The message has an MTI (0100 auth, 0200 financial), a bitmap marking which data elements are present, and DEs: DE2 PAN, DE4 amount, DE7 transmission date/time, DE11 STAN, DE41 terminal ID, DE55 EMV data.
Authorization Messages
| MTI | Name | Direction | Description | Key DEs | Success DE39 |
|---|---|---|---|---|---|
0100 | Authorization Request | Acquirer → Issuer | Real-time check of card validity and available funds. No funds are moved yet. Pre-authorization for hotels, car rentals. | DE2, DE3, DE4, DE7, DE11, DE22, DE25, DE41, DE42, DE49, DE55 | n/a |
0110 | Authorization Response | Issuer → Acquirer | Issuer decision: approve, decline, or refer. If approved, authorization hold is placed on account. | DE2, DE3, DE4, DE7, DE11, DE38, DE39, DE55 | 00 |
0120 | Authorization Advice | Acquirer → Issuer | Informs issuer of a completed authorization. Used when terminal operated in stand-in or offline mode. | DE2, DE3, DE4, DE7, DE11, DE38, DE39, DE41, DE42 | n/a |
0130 | Authorization Advice Response | Issuer → Acquirer | Acknowledgment of the advice. Typically code 00 to confirm receipt. | DE11, DE39 | 00 |
Financial Messages
| MTI | Name | Direction | Description | Success DE39 |
|---|---|---|---|---|
0200 | Financial Request | Acquirer → Issuer | Combined authorization and clearing in one step. Used for ATM cash, PIN debit, and some prepaid transactions where funds move immediately. | n/a |
0210 | Financial Response | Issuer → Acquirer | Response to the financial request. Approval completes the transaction immediately (no separate clearing needed). | 00 |
0201 | Financial Advice | Acquirer → Issuer | Notifies the issuer of a completed financial transaction that was performed offline or in stand-in. | n/a |
0211 | Financial Advice Response | Issuer → Acquirer | Acknowledgment of the financial advice. | 00 |
Reversal Messages
| MTI | Name | Description | Required DEs |
|---|---|---|---|
0400 | Reversal Request | Cancels a previously authorized transaction. Sent by acquirer when card is removed before approval, network timeout, or merchant void. DE90 contains original transaction data. | DE2, DE3, DE4, DE11, DE38, DE39, DE41, DE42, DE90 |
0410 | Reversal Response | Issuer confirms the reversal and releases the hold on the cardholder's account. | DE11, DE39, DE90 |
0420 | Reversal Advice | Issued when the acquirer was unable to receive a response to an earlier reversal request (e.g., network failure). Retransmission of the reversal. | DE2, DE3, DE4, DE11, DE90 |
0430 | Reversal Advice Response | Acknowledgment of the reversal advice. | DE11, DE39 |
Reconciliation & Network Management
| MTI | Name | DE70 Value | Description |
|---|---|---|---|
0500/0510 | Reconciliation Request/Response | n/a | End-of-day balancing. Acquirer submits totals; issuer confirms they match. Discrepancies trigger investigation. |
0800/0810 | Network Management Request/Response | 001 = Sign-on | Terminal or acquirer signs on to the network. Establishes session at start of business day. |
0800/0810 | Network Management Request/Response | 002 = Sign-off | Terminal signs off from the network. Sent at end of business day. |
0800/0810 | Network Management Request/Response | 301 = Echo test | Heartbeat / keepalive. Sent periodically to verify the link is alive. Response confirms connectivity. |
0800/0810 | Network Management Request/Response | 161 = Key exchange | Distributes new PIN encryption keys (working keys) derived from master keys. Run daily or per-session. |