9F0A

Application Selection Registered Proprietary Data is a mechanism for a card to signal, during application selection itself, support for proprietary features that go beyond what the standard selection tags, the AID in 4F and the label in 50, both covered earlier, communicate - a registered extension point specifically scoped to the selection phase of the transaction, before GPO or any acquisition tag exists yet. Because it's registered, meaning its use follows an EMVCo-administered registration process rather than being an arbitrary free-for-all, a terminal encountering 9F0A knows at least that the proprietary content follows some registered convention, even without necessarily knowing what that specific convention says - which is a meaningfully different situation from an entirely unregistered, issuer-arbitrary field like Application Discretionary Data (9F05, covered earlier). A terminal that doesn't recognise the specific registration a given 9F0A value refers to should simply ignore it rather than error out, since its entire design intent is additive, signalling extra capability without breaking terminals that don't understand it. See EMV 4.4 Book 3.