ISO 8583

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ISO 8583 Standard for Financial Transaction Card Originated Messages - Interchange message specifications is the International Organization for Standardization standard for systems that exchange electronic transactions made by cardholders using payment cards.


Contents

[edit] Introduction

A card-based transaction typically travels from a transaction acquiring device, such as a point-of-sale terminal or an 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. The card issuing system will either authorize or decline the transaction and generate a response message which must be delivered back to the terminal in a timely manner.1

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

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.

Although ISO 8583 defines a common standard, it is not typically used directly by systems or networks. Instead, each network adapts the standard for its own use with custom fields and custom usages.

The placement of fields in different versions of the standard varies; for example, the currency elements of the 1987 and 1993 versions are no longer used in the 2003 version, which holds currency as a sub-element of any financial amount element. As of writing, ISO 8583:2003 has yet to achieve wide acceptance.

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 fields of the message

[edit] Message Type Indicator (MTI)

This is a 4 digit numeric field which classifies the high level function of the message. A Message Type Indicator includes the ISO 8583 version, the Message Class, the Message Function and the Message Origin, each described briefly in the following sections.

example :

[edit] 0110

  0---> version of ISO 8583

(1987 version)

  -1--> class of the Message

(Authorization Message)

  --1-> function of the Message

(Request Response)

  ---0> who is began the communication

(Acquirer)



[edit] ISO 8583 Version

Position one of the MTI specifies the versions of the ISO 8583 standard which is being used to transmit the message.

Position Meaning
0xxx ISO 8583-1:1987 version
1xxx ISO 8583-2:1993 version
2xxx ISO 8583-1:2003 version
9xxx Private usage

[edit] Message Class

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

Position Meaning Usage
x1xx Authorization Message Determine if funds are available, get an approval but do not post to account for reconciliation, Dual Message System (DMS) system, awaits file exchange for posting to account
x2xx Financial Message Determines 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 Message Reverses the action of a previous authorization
x5xx Reconciliation Message Transmits settlement information
x6xx Administrative Message Transmits administrative advice. Often used for failure messages (e.g. message reject or failure to apply)
x7xx Fee Collection Message
x8xx Network Management Message Used for secure key exchange, logon, echo test and other network functions
x9xx Reserved by ISO

[edit] 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 timeouts and automatic reversals in place), while advices are point-to-point messages (eg, from terminal to acquirer, from acquirer to network, from network to issuer, with transmission guaranteed over each link, but not necessarily immediately).

Position Meaning
xx0x Request
xx1x Request Response
xx2x Advice
xx3x Advice Response
xx4x Notification
xx8x Response acknowledgment
xx9x Negative acknowledgment

[edit] Message Origin

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

Position Meaning
xxx0 Acquirer
xxx1 Acquirer Repeat
xxx2 Issuer
xxx3 Issuer Repeat
xxx4 Other
xxx5 Other Repeat

[edit] Examples

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
0120 Authorization Advice When the Point of Sale device breaks down and you have to sign a voucher
0121 Authorisation Advice Repeat if the advice times out
0200 Acquirer Financial Request Request for funds, typically from an ATM
0220 Acquirer Financial Advice e.g. Checkout at a hotel
0221 Acquirer Financial Advice repeat if the advice times out
0400 Acquirer Reversal Request Reverses a transaction
0420 Acquirer Reversal Advice Advises that a reversal has taken place
0421 Acquirer Reversal Advice Repeat Message if the reversal times out
0800 Network Management Request Echo test, logon, log off etc
0820 Network Management Advice Keychange

[edit] Bitmaps

Within ISO 8583, a bitmap is a field or subfield within a message which indicates which other data elements or data element subfields may be present elsewhere in a message.

A message will contain at least one bitmap, called the Primary Bitmap which indicates which of Data Elements 1 to 64 are present. A secondary bitmap may also be present, generally as data element one and indicates which of data elements 65 to 128 are present. Similarly, a tertiary, or third, bitmap can be used to indicate the presence or absence of fields 129 to 192, although these data elements are rarely used.

The bitmap may be transmitted as 8 bytes of binary data, or as 16 bytes of hexadecimal characters 0-9, A-F in the ASCII or EBCDIC character sets.

A field is present when the specific bit in the bitmap is true, i.e. byte '42x is binary '0100 0010' which means fields 2 and 7 are present in the message

[edit] Examples

Bitmap Defines presence of
4210001102C04804 Fields 2, 7, 12, 28, 32, 39, 41, 42, 50, 53, 62
7234054128C28805 Fields 2, 3, 4, 7, 11, 12, 14, 22, 24, 26, 32, 35, 37, 41, 42, 47, 49, 53, 62, 64 ,100 (Secondary Bitmap required to show the presense of field - 100)
8000000000000001 Field 1, 64
0000000000000003
(secondary bitmap)		 Fields 127, 128

[edit] 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 4909 and ISO 7813.

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 Fixed length
LLVAR or (..xx) Where xx < 100, means two leading digits specify the field length
LLLVAR or (...xxx) Where xxx < 1000, means three leading digits specify the field length
An LLVAR or LLLVAR field can be compressed or ascii depending of the message format which can be ASCII or Compressed. For example an LLVAR field can be 1 or 2 bytes, if compressed hex '23x means there are 23 elements to follow, if ascii, bytes '32x, '31x mean there are 21 elements to follow. An element depends on the data type, if numeric it will be compressed, e.g. length 87 will be represented by byte '87x, if ASCII then two bytes will follow, '38x, '37x. LLLVAR fields use 2 or 3 bytes (depending on message type) with a leading '0' nibble if compressed.
ISO-Defined Data Elements
Data Element Type Usage
1 b 64 Bit Map Extended
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 Systems trace audit number
12 n 6 Time, Local transaction
13 n 4 Date, Local transaction
14 n 4 Date, Expiration
15 n 4 Date, Settlement
16 n 4 Date, conversion
17 n 4 Date, capture
18 n 4 Merchant type
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 number
24 n 3 Function code(ISO 8583:1993)/Network International identifier (?)
25 n 2 Point of service condition code
26 n 2 Point of service capture code
27 n 1 Authorizing identification response length
28 n 8 Amount, transaction fee
29 n 8 Amount. settlement fee
30 n 8 Amount, transaction processing fee
31 n 8 Amount, settlement processing fee
32 n ..11 Acquiring institution identification code
33 n ..11 Forwarding institution identification code
34 n ..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
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 3 Currency code, transaction
50 an 3 Currency code, settlement
51 a 3 Currency code, cardholder billing
52 b 16 Personal Identification number data
53 n 18 Security related control information
54 an 120 Additional amounts
55 ans ..999 Reserved ISO
56 ans ..999 Reserved ISO
57 ans ..999 Reserved National
58 ans ..999 Reserved National
59 ans ..999 Reserved for national use
60 an ..7 Advice/reason code (private reserved)
61 ans ..999 Reserved Private
62 ans ..999 Reserved Private
63 ans ..999 Reserved Private
64 b 16 Message authentication code (MAC)
65 b 16 Bit map, tertiary
66 n 1 Settlement code
67 n 2 Extended payment code
68 n 3 Receiving institution country code
69 n 3 Settlement institution county code
70 n 3 Network management Information code
71 n 4 Message number
72 ans ..999 Data record (ISO 8583:1993)/n 4 Message number, last(?)
73 n 6 Date, Action
74 n 10 Credits, number
75 n 10 Credits, reversal number
76 n 10 Debits, number
77 n 10 Debits, reversal number
78 n 10 Transfer number
79 n 10 Transfer, reversal number
80 n 10 Inquiries number
81 n 10 Authorizations, number
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 15 Credits, amount
87 n 15 Credits, reversal amount
88 n 15 Debits, amount
89 n 15 Debits, reversal amount
90 n 42 Original data elements
91 an 1 File update code
92 n 2 File security code
93 n 5 Response indicator
94 an 7 Service indicator
95 an 42 Replacement amounts
96 an 8 Message security code
97 n 16 Amount, net settlement
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 Reserved for ISO use
107 ans ..999 Reserved for ISO use
108 ans ..999 Reserved for ISO use
109 ans ..999 Reserved for ISO use
110 ans ..999 Reserved for ISO use
111 ans ..999 Reserved for ISO use
112 ans ..999 Reserved for national use
113 n ..11 Authorizing agent institution id code
114 ans ..999 Reserved for national use
115 ans ..999 Reserved for national use
116 ans ..999 Reserved for national use
117 ans ..999 Reserved for national use
118 ans ..999 Reserved for national use
119 ans ..999 Reserved for national use
120 ans ..999 Reserved for private use
121 ans ..999 Reserved for private use
122 ans ..999 Reserved for private use
123 ans ..999 Reserved for private use
124 ans ..255 Info Text
125 ans ..50 Network management information
126 ans ..6 Issuer trace id
127 ans ..999 Reserved for private use
128 b 16 Message Authentication code

[edit] Examples

Field Definition Meaning
n6 Fixed length field of six digits
n.6 LVAR numeric field of up to 6 digits in length
a..11 LLVAR alphanumeric field of up to 11 characters in length
b...999 LLLVAR binary field of up to 999 bytes in length

[edit] External links

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