If a client does not show up to their appointment (and hasn't cancelled or asked you to cancel on their behalf), you can mark it as a no-show to ensure it's documented and recorded for future reference.
Go to the "Calendar" tab
Right-click the appointment you want to mark as a No-Show
Click "No-Show!" as show below:
Notes
No-show appointments are colored purple:
You can undo a no-show at any time by right-clicking the appointment, then clicking "Undo No-show!"
No-show appointments are included in the appointment report and the appointment status metric report exports.
You may also mark appointments as no-show in the client's booking history in the Clients tab.