ISO 8583 · Data fields

Field 102Account ID 1

pyiso8583 starter profilesIndependent explanation

What this field describes

This is the first account ID container in the selected profiles.

The implementation decides which account role it represents. Do not assume it contains a card account number.

Compare the two profiles

Container settings from the pinned pyiso8583 source.
Setting	`default`	`default_ascii`
Value encoding	ASCII	ASCII
Length limit	Up to 28 bytes	Up to 28 bytes
Prefix	2 ASCII bytes	2 ASCII bytes

Length limits describe encoded values. They exclude any length prefix. The profiles can be customized; these settings do not establish the required fields or accepted values for a live connection.

Read the field boundary

Length prefix2 bytesASCII length

Field 102≤ 28 bytesASCII value

Read the 2 prefix bytes first, then read that many value bytes. Reject a length that exceeds 28 or the bytes remaining in the message.

Find it in the bitmap

Bitmap: Secondary
Position: 38
Byte: 5
Bit in byte: 6

Positions start at one. Bits are counted from the most significant bit of each bitmap byte. This calculation locates the field’s presence indicator, not its value.