A booking reference code (8-digit code) can be generated for each appointment.
This code will appear in the email confirmation automatically, that is sent to you.
In order to send the booking reference to the appointment booker, you can insert the placeholder "REFERENCECODE" in the email confirmation:
Also you could activate the QR code in the appointment confirmation email for such use cases, so that the unique appointment ID can be checked accordingly using the QR reader.
For example you can use this HTML Code with the placeholder QRCODE in your email confirmation template:
<img style="border: none" src="QRCODE">