ISO 8583 · Data fields

Field 18Merchant Type

pyiso8583 starter profilesIndependent explanation

What this field describes

This field is labelled Merchant Type in the starter profiles and has a four byte container.

The starter profiles do not supply the permitted merchant classification list. Use the classification source named by the acquiring connection.

Compare the two profiles

Container settings from the pinned pyiso8583 source.
Setting	`default`	`default_ascii`
Value encoding	ASCII	ASCII
Length limit	Exactly 4 bytes	Exactly 4 bytes
Prefix	None	None

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

Field 184 bytesASCII value

Read exactly 4 value bytes. The next field begins immediately afterwards under this profile; no length prefix belongs to this field.

Find it in the bitmap

Bitmap: Primary
Position: 18
Byte: 3
Bit in byte: 2

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.