Acquiring Institution Identification Code
What it is
Identifies the acquirer (or its processor) that introduced the transaction into the network.
The acquirer ID identifies which member institution acquired the transaction — it drives settlement position calculation and appears again in reversals and chargebacks so the original acquirer can be found. Together with DE 33 it traces the acquiring path when intermediate processors forward messages.
DE 32 on the wire
Bitmap position
DE 32 is bit 32 of the primary bitmap: byte 4, mask 0x01. A primary bitmap with only DE 32 present reads 0000000100000000 in hex.
Length
DE 32 is variable length (LLVAR): a 2-digit prefix gives the length of the value in digits, from 0 to 11. A 11-digit value is sent as 11 followed by the value. In ASCII the prefix is the bytes 31 31; dialects that pack lengths as BCD send 11 instead.
Size in the message
At most 13 bytes when the message travels as text (ASCII or EBCDIC), or 7 bytes in binary dialects that pack digits as BCD.
Format n
Format n means numeric: the digits 0–9 only.
Specification reference
Defined in ISO 8583:1987 (base). Card networks publish their own dialect tables (Visa BASE I / V.I.P., Mastercard CIS) that refine formats, lengths, and — for private-use elements — the entire layout. Always confirm against the interface specification you implement.