Aug 232017

ADM

ISO8583 financial transaction message format

  • August 23 2017
  • ADM

 

 

ISO8583 financial transaction message format - eft

 

When is about card initiated transactions is about ISO 8583 financial transaction message format standard.

Introduction

Usually, a card initiated transaction travels from a point-of-sale terminal (POS) or an automated teller machine (ATM), using a series of networks to the card issuer entity for authorization against the card holder's account. The transaction data contains information from the card (PAN, expiry date), from the terminal (transaction number, merchant data) and information added dynamically during the process and by the intervening systems. The card issuer entity will authorize or decline the transaction and generate a response message which must be delivered back to the POS or ATM within a predefined time period (usual this period is 30 sec).

In this chain of systems from the terminal (POS or ATM) to the card issuer entity and back usually is used ISO 8583 message format. Although ISO 8583 defines a common standard, different systems may use the fields in different ways because only some fields are standards fields and the meaning is the same for all systems. Some of the fields are generic and can be used by each entity in a custom way.

There are few versions of the ISO 8583 standard: ISO 8583:1987, ISO 8583:1993, ISO 8583:2003. 1987 and 1993 versions are very similar and version 2003 is very different and was created to be more generic. In this tutorial, I will concentrate on ISO 8583:1987 version, as is still the most widely used. The main idea is the same for all versions. The differences are on fields levels and meanings.

Message Format

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.

Message type identifier

Primary bitmap

Secondary bitmap

Data elements

Message Type Identifier (MTI)

Message Type Identifier is a key element which classifies the function of the message. MTI is a 4 digits long field and each digits have its own meaning:

  • First digit: ISO 8583 version;
  • Second digit: Message Class;
  • Third digit: Message Function;
  • Fourth digit: Message Origin.

ISO 8583 version

Currently there are 3 versions.

Position Meaning
0xxx ISO 8583:1987
1xxx ISO 8583:1993
2xxx ISO 8583:2003

Message Class

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

Position 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.
x2xx Financial messages Determine if funds are available, get an approval and post directly to the account.
x3xx File Actions Message Used for hot-card, TMS and other exchanges
x4xx Reversal and Chargeback Messages Reverses the action of a previous authorization.
x5xx. Reconciliation Message Transmits settlement information message.
x6xx Administrative Message Transmits administrative advice.
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.

Position Meaning
xx0x Request
xx1x Request response
xx2x Advice
xx3x Advice Response
xx4x Notification
xx5x Notification Acknowledgement
xx6x Instruction (ISO 8583:2003 only)
xx7x Instruction Acknowledgement (ISO 8583:2003 only)
xx8x Reserved for ISO use.
xx9x Reserved for ISO use.

Message origin

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

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

Examples

Here is a list with some MTI and the usage.

MTI Meaning Usage
0100 Authorization Request Request from a point-of-sale terminal for authorization a purchase
0110 Request Response Request response to a point-of-sale terminal for authorization a purchase
0101 Authorization Request Repeat If the Authorization Request times out
0200 Acquirer Financial Request Request for funds, e.g. from an ATM.
0210 Issuer Response to Financial Request Issuer response to request for funds
0220 Acquirer Financial Advice 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
0400 Acquirer Reversal Request Reverses a transaction
0820 Network Management Advice Keychange

Bitmaps

Next area in the ISO8583 message is bitmaps area. A bitmap is a field indicates which data elements may be present or not in the 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 as data element one and indicates which of data elements 65 to 128 are present. Also, a third bitmap can be used to indicate the presence or absence of fields 129 to 192.

Example

Bitmap Binary value Defines presence of
7200000008C00000 01110010000000000000000000000000 00001000110000000000000000000000 Fields 2, 3, 4, 7, 37, 41, 42

Note: the first bit of each bitmap signifies the presence of the next bitmap.

Data Elements

Data elements are all the fields that contain the transaction information. ISO8583:1997 contains up to 128 data elements (the message will have up to 2 bitmap fields). The later versions contain up to 192 data elements (the message will have up to 3 bitmaps fields). Each field (data element) has a specific meaning and format: some are for general purpose or system related fields or country specific fields.

Format

Each field is described in a standard format which defines the content format or the field length.

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.
. or .. or ... variable field length indicator, each. indicating a digit.
x or xx or xxx fixed length of the field or maximum length in the case of variable length fields.

ISO-defined data elements

Data Field Type Usage
1 b 64 Bit map (b 128 if secondarily is present and b 192 if tertiary is present)
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 Time, local transaction (hhmmss)
13 n 4 Date, local transaction (MMDD)
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 sequence number
24 n 3 Function code (ISO 8583:1993)/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 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 64 Personal identification number data
53 n 16 Security related control information
54 an ...120 Additional amounts
55 ans ...999 Reserved ISO
56 ans ...999 Reserved ISO
57-60 ans ...999 Reserved national
61-63 ans ...999 Reserved private
64 b 16 Message authentication code (MAC)
65 b 1 Bitmap, extended
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 Message number, last
73 n 6 Date, action (YYMMDD)
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 16 Credits, amount
87 n 16 Credits, reversal amount
88 n 16 Debits, amount
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 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
105-111 ans ...999 Reserved for ISO use
112-119 ans ...999 Reserved for national use
120-127 ans ...999 Reserved for private use
128 b 64 Message authentication code