To facilitate conducting a secure transaction via wireless communication between a portable electronic device (such as a smartphone) and another electronic device (such as a point-of-sale terminal), the portable electronic device may, after a final command is received from the other electronic device, determine a unique transaction identifier for the secure transaction. In particular, the final command may be specific to an applet, stored in a secure element in the portable electronic device, which conducts the secure transaction. The secure element may generate the unique transaction identifier based on financial-account information associated with the applet, which is communicated to the other electronic device. Next, the secure element may provide, to a processor in the portable electronic device, an end message for the secure transaction with the unique transaction identifier.