9F1F

Track 1 Discretionary Data is the portion of the chip-carried Track 1 (56, covered earlier) that ISO/IEC 7813 leaves open for issuer-specific content, rather than the standardised PAN, name, and expiry fields the rest of the track defines - the same discretionary-data concept magnetic-stripe processing has used for decades, just carried into the chip's own copy of the track. It's related to Track 2 Discretionary Data (9F20), the equivalent field for the other track, and the two together are where a surprising amount of legacy, issuer-specific logic actually lives - CVV/CVC values, service-code-adjacent flags, or other host-specific content that predates EMV and that a host built for the stripe era still expects to find in exactly this position. Because it's explicitly discretionary, its contents aren't standardised by EMV at all; a terminal or analysis tool has to know the specific issuer or scheme's own layout to interpret it meaningfully, and treating it as a fixed, universal structure across different issuers is a common source of misparsing. See EMV 4.4 Book 3.