Format: nLength: 1Fixed length
DE 66
Settlement Code
What it is
Result of a settlement request (0500/0510 messages).
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.