You can cancel sending a fax using either the machine's control panel or your computer, depending on the status of the job.
Canceling while the machine is receiving a fax from the computer
If the machine is shared by multiple computers, be careful not to cancel the fax of another user.
Double-click the printer icon on the task bar of your computer.
Select the print job you want to cancel, click the [Document] menu, and then click [Cancel].
Canceling while sending a fax
Cancel the fax using the control panel.
Press the [Facsimile] key.
Press the [Clear/Stop] key.