9B

Tag 9B answers a different question from the one most people bring to it. Where the Terminal Verification Results records what the terminal found, the Transaction Status Information records what the terminal actually did. Two bytes, one bit per function, and only byte 1 carries meaning — byte 2 is reserved end to end.

The six defined bits map onto the major stages of the transaction: offline data authentication was performed, cardholder verification was performed, card risk management was performed, issuer authentication was performed, terminal risk management was performed, script processing was performed. Note the tense. Every one of them is a statement about the past, and none of them says whether the function succeeded. The TSI tells you a stage ran; the TVR tells you how it went.

Reading the two together is what makes either useful, and the pairing resolves a whole class of confusion. If a TVR bit for a failed authentication is clear, that could mean authentication passed — or it could mean authentication never ran at all. The TSI settles it: if bit 8 of byte 1 is off, offline data authentication did not happen, and the clear TVR bit says nothing about the card. Likewise, an issuer script that appears to have done nothing is a different problem depending on whether TSI byte 1 bit 3 is on. If script processing never ran, look at the terminal configuration and the online response; if it ran, look at the script itself.

The value E800 is worth internalising because it describes an ordinary transaction. It sets four bits: offline data authentication performed, cardholder verification performed, card risk management performed, and terminal risk management performed. Issuer authentication and script processing are both off, which is exactly what you expect from a transaction that was approved offline, or that went online without the issuer returning authentication data. Nothing about E800 is an error — it is the shape of a transaction that ran its offline stages and stopped there.