ISO 8583 · Data fields

Field 2Primary Account Number (PAN)

pyiso8583 starter profilesIndependent explanation

What this field describes

This container carries the primary account number in these profiles. Its two character length prefix allows the value to vary in length.

Keep the value as text to preserve leading zeros. Use masked or synthetic data in documentation and diagnostics.

Compare the two profiles

Container settings from the pinned pyiso8583 source.
Settingdefaultdefault_ascii
Value encodingASCIIASCII
Length limitUp to 19 bytesUp to 19 bytes
Prefix2 ASCII bytes2 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 2≤ 19 bytesASCII value

Read the 2 prefix bytes first, then read that many value bytes. Reject a length that exceeds 19 or the bytes remaining in the message.

Find it in the bitmap

Bitmap
Primary
Position
2
Byte
1
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.