Format: ansLength: ...999Variable (LLLVAR — 3-digit length prefix)
DE 62
Reserved — Private (Custom/Trace)
What it is
Private use. Visa: custom payment service fields (transaction ID). Mastercard: intermediate network data.
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.