ISO 8583

ISO 8583 is an international standard for financial transaction card originated interchange messaging. It is the International Organization for Standardization standard for systems that exchange electronic transactions initiated by cardholders using payment cards.

ISO 8583 defines a message format and a communication flow so that different systems can exchange these transaction requests and responses. The vast majority of transactions made when a customer uses a card to make a payment in a store (EFTPOS) use ISO 8583 at some point in the communication chain, as do transactions made at ATMs. In particular, both the MasterCard and Visa networks base their authorization communications on the ISO 8583 standard, as do many other institutions and networks.

Although ISO 8583 defines a common standard, it is not typically used directly by systems or networks. It defines many standard fields (data elements) which remain the same in all systems or networks, and leaves a few additional fields for passing network-specific details. These fields are used by each network to adapt the standard for its own use with custom fields and custom usages.

Introduction

The ISO 8583 specification has three parts:

• Part 1: Messages, data elements, and code values
• Part 2: Application and registration procedures for Institution Identification Codes (IIC)
• Part 3: Maintenance procedures for the aforementioned messages, data elements and code values

Message format

A card-based transaction typically travels from a transaction-acquiring device, such as a point-of-sale terminal or an automated teller machine (ATM), through a series of networks, to a card issuing system for authorization against the card holder's account. The transaction data contains information derived from the card (e.g., the account number), the terminal (e.g., the merchant number), the transaction (e.g., the amount), together with other data which may be generated dynamically or added by intervening systems. Based on this information, the card issuing system will either authorize or decline the transaction and generate a response message which must be delivered back to the terminal within a predefined time period.

An ISO 8583 message is made of the following parts:

• Message type indicator (MTI)
• One or more bitmaps, indicating which data elements are present
• Data elements, the actual information fields of the message

The placements of fields in different versions of the standard varies; for example, the currency elements of the 1987 and 1993 versions of the standard are no longer used in the 2003 version, which holds currency as a sub-element of any financial amount element. As of June 2017, however ISO 8583:2003 has yet to achieve wide acceptance. ISO 8583 messaging has no routing information, so is sometimes used with a TPDU header.

Cardholder-originated transactions include purchase, withdrawal, deposit, refund, reversal, balance inquiry, payments and inter-account transfers. ISO 8583 also defines system-to-system messages for secure key exchanges, reconciliation of totals, and other administrative purposes.

Message type indicator (MTI)

The message type indicator is a four-digit numeric field which indicates the overall function of the message. A message type indicator includes the ISO 8583 version, the Message Class, the Message Function and the Message Origin, as described below.

ISO 8583 version

The first digit of the MTI indicates the ISO 8583 version in which the message is encoded.

Code	Meaning
0xxx	ISO 8583:1987
1xxx	ISO 8583:1993
2xxx	ISO 8583:2003
3xxx	Reserved by ISO
4xxx
5xxx
6xxx
7xxx
8xxx	National use
9xxx	Private use

Message class

Position two of the MTI specifies the overall purpose of the message.

Code	Meaning	Usage
x0xx	Reserved by ISO
x1xx	Authorization message	Determine if funds are available, get an approval but do not post to account for reconciliation. Dual message system (DMS), awaits file exchange for posting to the account.
x2xx	Financial messages	Determine if funds are available, get an approval and post directly to the account. Single message system (SMS), no file exchange after this.
x3xx	File actions message	Used for hot-card, TMS and other exchanges
x4xx	Reversal and chargeback messages	Reversal (x4x0 or x4x1): Reverses the action of a previous authorization. Chargeback (x4x2 or x4x3): Charges back a previously cleared financial message.
x5xx	Reconciliation message	Transmits settlement information message.
x6xx	Administrative message	Transmits administrative advice. Often used for failure messages (e.g. message reject or failure to apply).
x7xx	Fee collection messages
x8xx	Network management message	Used for secure key exchange, logon, echo test and other network functions.
x9xx	Reserved by ISO

Message function

Position three of the MTI specifies the message function which defines how the message should flow within the system. Requests are end-to-end messages (e.g., from acquirer to issuer and back with time-outs and automatic reversals in place), while advices are point-to-point messages (e.g., from terminal to acquirer, from acquirer to network, from network to issuer, with transmission guaranteed over each link, but not necessarily immediately).

Code	Meaning	Notes
xx0x	Request
xx1x	Request response
xx2x	Advice
xx3x	Advice response
xx4x	Notification
xx5x	Notification acknowledgement
xx6x	Instruction	ISO 8583:2003 only
xx7x	Instruction acknowledgement
xx8x	Reserved for ISO use	Some implementations (such as MasterCard) use for positive acknowledgment.
xx9x		Some implementations (such as MasterCard) use for negative acknowledgement.

Message origin

Position four of the MTI defines the location of the message source within the payment chain.

Code	Meaning
xxx0	Acquirer
xxx1	Acquirer repeat
xxx2	Issuer
xxx3	Issuer repeat
xxx4	Other
xxx5	Other repeat
xxx6	Reserved by ISO
xxx7
xxx8
xxx9

Examples

Given an MTI value of 0110, the following example lists what each position indicates:

• 0xxx → version of ISO 8583 (0 = 1987 version)
• x1xx → class of the message (1 = authorization message)
• xx1x → function of the message (1 = response)
• xxx0 → who began the communication (0 = acquirer)

Therefore, MTI 0110 is an authorization response message sent by the acquirer.

Bearing each of the above four positions in mind, an MTI will completely specify what a message should do, and how it is to be transmitted around the network. Unfortunately, not all ISO 8583 implementations interpret the meaning of an MTI in the same way. However, a few MTIs are relatively standard:

MTI	Meaning	Usage
0100	Authorization Request	Request from a point-of-sale terminal for authorization for a cardholder purchase
0110	Authorization Response	Request response to a point-of-sale terminal for authorization for a cardholder purchase
0120	Authorization Advice	When the point-of-sale device breaks down and you have to sign a voucher
0121	Authorization Advice Repeat	If the advice times out
0130	Issuer Response to Authorization Advice	Confirmation of receipt of authorization advice
0200	Acquirer Financial Request	Request for funds, typically from an ATM or pinned point-of-sale device
0210	Issuer Response to Financial Request	Issuer response to request for funds
0220	Acquirer Financial Advice	e.g. Checkout at a hotel. Used to complete transaction initiated with authorization request
0221	Acquirer Financial Advice Repeat	If the advice times out
0230	Issuer Response to Financial Advice	Confirmation of receipt of financial advice
0320	Batch Upload	File update/transfer advice
0330	Batch Upload Response	File update/transfer advice response
0400	Acquirer Reversal Request	Reverses a transaction
0510	Batch Settlement response	Card acceptor reconciliation request response
0800	Network Management Request	Hypercom terminals initialize request. Echo test, logon, logoff etc.
0810	Network Management Response	Hypercom terminals initialize response. Echo test, logon, logoff etc.
0820	Network Management Advice	Key change

Bitmaps

In ISO 8583, a bitmap is a field or subfield within a message, which indicates whether other data elements or data element subfields are present elsewhere in the message.

A field is considered to be present only when the corresponding bit in the bitmap is set. For example, a hex with value 0x82 (decimal 130) is binary 1000 0010, which means fields 1 and 7 are present in the message and fields 2, 3, 4, 5, 6 and 8 are not.

The bitmap may be represented as 8 bytes of binary data or as 16 hexadecimal characters (0-9, A-F) in the ASCII or EBCDIC character sets. A message will contain at least one bitmap, called the primary bitmap, which indicates which of data elements 1 to 64 are present. The presence of an optional secondary bitmap is also indicated by the first bit in the primary bitmap. If present, the secondary bitmap indicates whether data elements 65 to 128 are present. Similarly, a tertiary bitmap can be used to indicate the presence of fields 129 to 192, although these data elements are rarely used.

Examples

Given a bitmap value of 22 10 00 11 02 C0 48 04,

0x22 = 0010 0010 (counting from the left, the third and seventh bits are 1, indicating that fields 3 and 7 are present)

0x10 = 0001 0000 (the first bit corresponds to field 9, so the fourth bit here indicates field 12 is present)

0x00 = 0000 0000 (no fields present)

0x11 = 0001 0001 (fields 28 and 32 are present)

0x02 = 0000 0010 (field 39 is present)

0xC0 = 1100 0000 (fields 41 and 42 are present)

0x48 = 0100 1000 (fields 50 and 53 are present)

0x04 = 0000 0100 (field 62 is present)

nth bit	0	10	20	30	40	50	60
	1234567890	1234567890	1234567890	1234567890	1234567890	1234567890	1234
Bitmap	0010001000	0100000000	0000000100	0100000010	1100000001	0010000000	0100

Therefore, the given bitmap defines the following fields present in the message:
3, 7, 12, 28, 32, 39, 41, 42, 50, 53, 62

Data elements

Data elements are the individual fields carrying the transaction information. There are up to 128 data elements specified in the original ISO 8583:1987 standard, and up to 192 data elements in later releases. The 1993 revision added new definitions, deleted some, while leaving the message format itself unchanged.

While each data element has a specified meaning and format, the standard also includes some general purpose data elements and system- or country-specific data elements which vary enormously in use and form from implementation to implementation.

Each data element is described in a standard format which defines the permitted content of the field (numeric, binary, etc.) and the field length (variable or fixed), according to the following table:

Abbreviation	Meaning
a	Alpha, including blanks
n	Numeric values only
s	Special characters only
an	Alphanumeric
as	Alpha & special characters only
ns	Numeric and special characters only
ans	Alphabetic, numeric and special characters.
b	Binary data
z	Tracks 2 and 3 code set as defined in ISO/IEC 7813 and ISO/IEC 4909 respectively
. or .. or ...	variable field length indicator, each . indicating a digit.
x or xx or xxx	fixed length of field, or maximum length in the case of variable length fields.

Additionally, each field may be either fixed or variable length. If variable, the length of the field will be preceded by a length indicator.

Type	Meaning
Fixed	no field length used
LLVAR or (..xx)	Where 0 < LL < 100, means two leading digits LL specify the field length of field VAR
LLLVAR or (...xxx)	Where 0 < LLL < 1000, means three leading digits LLL specify the field length of field VAR
LL and LLL are hex or ASCII. A VAR field can be compressed or ASCII depending of the data element type.	LL can be one or two bytes. For example, if compressed as one hex byte, '27x means there are 27 VAR bytes to follow. If ASCII, the two bytes '32x, '37x mean there are 27 bytes to follow. Three-digit field length LLL uses two bytes with a leading '0' nibble if compressed, or three bytes if ASCII. The format of a VAR data element depends on the data element type. If numeric it will be compressed, e.g. 87456 will be represented by three hex bytes '087456x. If ASCII then one byte for each digit or character is used, e.g. '38x, '37x, '34x, '35x, '36x.

Examples

Field Definition	Meaning
n 6	Fixed length field of six digits
n.6	LVAR numeric field of up to 6 digits in
a..11	LLVAR alpha field of up to 11 characters in length
b...999	LLLVAR binary field of up to 999 bits in length

ISO-defined data elements

Data field	Type	Usage
1	b 64	Second Bitmap
2	n ..19	Primary account number (PAN)
3	n 6	Processing code
4	n 12	Amount, transaction
5	n 12	Amount, settlement
6	n 12	Amount, cardholder billing
7	n 10	Transmission date & time
8	n 8	Amount, cardholder billing fee
9	n 8	Conversion rate, settlement
10	n 8	Conversion rate, cardholder billing
11	n 6	System trace audit number (STAN)
12	n 6	Local transaction time (hhmmss)
13	n 4	Local transaction date (MMDD)
14	n 4	Expiration date
15	n 4	Settlement date
16	n 4	Currency conversion date
17	n 4	Capture date
18	n 4	Merchant type, or merchant category code
19	n 3	Acquiring institution (country code)
20	n 3	PAN extended (country code)
21	n 3	Forwarding institution (country code)
22	n 3	Point of service entry mode
23	n 3	Application PAN sequence number
24	n 3	Function code (ISO 8583:1993), or network international identifier (NII)
25	n 2	Point of service condition code
26	n 2	Point of service capture code
27	n 1	Authorizing identification response length
28	x+n 8	Amount, transaction fee
29	x+n 8	Amount, settlement fee
30	x+n 8	Amount, transaction processing fee
31	x+n 8	Amount, settlement processing fee
32	n ..11	Acquiring institution identification code
33	n ..11	Forwarding institution identification code
34	ns ..28	Primary account number, extended
35	z ..37	Track 2 data
36	n ...104	Track 3 data
37	an 12	Retrieval reference number
38	an 6	Authorization identification response
39	an 2	Response code
40	an 3	Service restriction code
41	ans 8	Card acceptor terminal identification
42	ans 15	Card acceptor identification code
43	ans 40	Card acceptor name/location (1-23 street address, 24-36 city, 37-38 state, 39-40 country)
44	an ..25	Additional response data
45	an ..76	Track 1 data
46	an ...999	Additional data (ISO)
47	an ...999	Additional data (national)
48	an ...999	Additional data (private)
49	a or n 3	Currency code, transaction
50	a or n 3	Currency code, settlement
51	a or n 3	Currency code, cardholder billing
52	b 8	Personal identification number data
53	n 16	Security related control information
54	an ...120	Additional amounts
55	ans ...999	ICC data – EMV having multiple tags
56	ans ...999	Reserved (ISO)
57	ans ...999	Reserved (national)
58	ans ...999
59	ans ...999
60	ans ...999	Reserved (national) (e.g. settlement request: batch number, advice transactions: original transaction amount, batch upload: original MTI plus original RRN plus original STAN, etc)
61	ans ...999	Reserved (private) (e.g. CVV2/service code   transactions)
62	ans ...999	Reserved (private) (e.g. transactions: invoice number, key exchange transactions: TPK key, etc.)
63	ans ...999	Reserved (private)
64	b 16	Message authentication code (MAC)
65	b 1	Extended bitmap indicator
66	n 1	Settlement code
67	n 2	Extended payment code
68	n 3	Receiving institution country code
69	n 3	Settlement institution country code
70	n 3	Network management information code
71	n 4	Message number
72	n 4	Last message's number
73	n 6	Action date (YYMMDD)
74	n 10	Number of credits
75	n 10	Credits, reversal number
76	n 10	Number of debits
77	n 10	Debits, reversal number
78	n 10	Transfer number
79	n 10	Transfer, reversal number
80	n 10	Number of inquiries
81	n 10	Number of authorizations
82	n 12	Credits, processing fee amount
83	n 12	Credits, transaction fee amount
84	n 12	Debits, processing fee amount
85	n 12	Debits, transaction fee amount
86	n 16	Total amount of credits
87	n 16	Credits, reversal amount
88	n 16	Total amount of debits
89	n 16	Debits, reversal amount
90	n 42	Original data elements
91	an 1	File update code
92	an 2	File security code
93	an 5	Response indicator
94	an 7	Service indicator
95	an 42	Replacement amounts
96	b 64	Message security code
97	x+n 16	Net settlement amount
98	ans 25	Payee
99	n ..11	Settlement institution identification code
100	n ..11	Receiving institution identification code
101	ans ..17	File name
102	ans ..28	Account identification 1
103	ans ..28	Account identification 2
104	ans ...100	Transaction description
105	ans ...999	Reserved for ISO use
106	ans ...999
107	ans ...999
108	ans ...999
109	ans ...999
110	ans ...999
111	ans ...999
112	ans ...999	Reserved for national use
113	ans ...999
114	ans ...999
115	ans ...999
116	ans ...999
117	ans ...999
118	ans ...999
119	ans ...999
120	ans ...999	Reserved for private use
121	ans ...999
122	ans ...999
123	ans ...999
124	ans ...999
125	ans ...999
126	ans ...999
127	ans ...999
128	b 64	Message authentication code

Processing code

The following is a table specifying the message type and processing code for each transaction type.

Transaction	Message type	Processing code
Authorization	0100	00 a0 0x
Balance inquiry		31 a0 0x
Sale	0200	00 a0 0x
Cash		01 a0 0x
Void		02 a0 0x
Mobile topup		57 a0 0x

Response code

The following table shows response codes and their meanings.

Code	Meaning
00	Successful approval/completion or that VIP PIN verification is valid
01	Refer to card issuer
02	Refer to card issuer, special condition
03	Invalid merchant or service provider
04	Pickup
05	Do not honor
06	General error
07	Pickup card, special condition (other than lost/stolen card)
08	Honor with identification
09	Request in progress
10	Partial approval
11	VIP approval
12	Invalid transaction
13	Invalid amount (currency conversion field overflow) or amount exceeds maximum for card program
14	Invalid account number (no such number)
15	No such issuer
16	Insufficient funds
17	Customer cancellation
19	Re-enter transaction
20	Invalid response
21	No action taken (unable to back out prior transaction)
22	Suspected Malfunction
25	Unable to locate record in file, or account number is missing from the inquiry
28	File is temporarily unavailable
30	Format error
41	Merchant should retain card (card reported lost)
43	Merchant should retain card (card reported stolen)
51	Insufficient funds
52	No checking account
53	No savings account
54	Expired card
55	Incorrect PIN
57	Transaction not permitted to cardholder
58	Transaction not allowed at terminal
59	Suspected fraud
61	Activity amount limit exceeded
62	Restricted card (for example, in country exclusion table)
63	Security violation
65	Activity count limit exceeded
68	Response received too late
75	Allowable number of PIN-entry tries exceeded
76	Unable to locate previous message (no match on retrieval reference number)
77	Previous message located for a repeat or reversal, but repeat or reversal data are inconsistent with original message
78	’Blocked, first used’—The transaction is from a new cardholder, and the card has not been properly unblocked.
80	Visa transactions: credit issuer unavailable. Private label and check acceptance: Invalid date
81	PIN cryptographic error found (error found by VIC security module during PIN decryption)
82	Negative CAM, dCVV, iCVV, or CVV results
83	Unable to verify PIN
85	No reason to decline a request for account number verification, address verification, CVV2 verification; or a credit voucher or merchandise return
91	Issuer unavailable or switch inoperative (STIP not applicable or available for this transaction)
92	Destination cannot be found for routing
93	Transaction cannot be completed, violation of law
94	Duplicate transmission
95	Reconcile error
96	System malfunction, System malfunction or certain field error conditions
B1	Surcharge amount not permitted on Visa cards (U.S. acquirers only)
N0	Force STIP
N3	Cash service not available
N4	Cashback request exceeds issuer limit
N7	Decline for CVV2 failure
P2	Invalid biller information
P5	PIN change/unblock request declined
P6	Unsafe PIN
Q1	Card authentication failed
R0	Stop payment order
R1	Revocation of authorization order
R3	Revocation of all authorizations order
XA	Forward to issuer
XD	Forward to issuer
Z3	Unable to go online

See also

• AS 2805
• Magnetic stripe card
• NCR Corporation
• Itautec
• Diebold