American Express ExpressPay — EMVCo Kernel 4
Amex ExpressPay (Kernel 4): no TTQ — the reader sends Enhanced Contactless Reader Capabilities (9F6E). Supports partial-online, delayed authorisation and Mobile CVM.
Overview
Kernel 4 is the EMVCo contactless kernel for American Express ExpressPay. It does not use a TTQ. Instead the reader sends the Enhanced Contactless Reader Capabilities (9F6E) — and optionally the legacy Contactless Reader Capabilities (9F6D) — in the GPO command.
ExpressPay supports several completion styles including partial online and delayed authorisation, and resolves cardholder verification through Mobile CVM Results (9F71) for wallet transactions.
Transaction flow
American Express ExpressPay (Kernel 4). Kernel 4 does not use a TTQ — the reader sends Enhanced Contactless Reader Capabilities (9F6E). It supports partial-online and delayed-authorisation flows and Mobile CVM.
1App Selection
PPSE → AID
Entry Point selects the Amex application and activates Kernel 4 (EMV mode only on modern readers).
Enhanced Contactless Reader Capabilities (9F6E)
The 4-byte 9F6E carries terminal capabilities (contact/contactless modes, mobile, Try-Another-Interface), CVM capabilities (mobile CVM, online PIN, signature, offline PIN), and transaction capabilities (offline-only, CVM required, delayed authorisation, transit).
Decode it live: Amex Reader Capabilities Decoder
Cardholder verification
CVM uses the 9F6E CVM-capability bits and, for mobile wallets, the Mobile CVM Results (9F71): mobile CVM, online PIN, signature, or plaintext offline PIN.
Key data elements
| Tag | Name | Notes |
|---|---|---|
9F6E | Enhanced Contactless Reader Capabilities | Amex meaning of 9F6E — the TTQ-equivalent. |
9F6D | Contactless Reader Capabilities | Legacy mag-stripe-mode capabilities. |
9F70 | Card Interface & Payment Capabilities | Amex card-side capabilities. |
9F71 | Mobile CVM Results | On-device CVM result for wallets. |