This button is on the Player. Clicking this button will close the dictation and move it from the folder where it was stored into the corresponding completed dictations folder. There is an option on the Options / Workflow tab to ask for a link to the written document (that was just typed-up), or other relevant files, whenever this button is pressed.
If you have the Philips LFH 2330 footswitch, this function is allocated to the smaller, upper- middle pedal.