Enable Room & Tax Posting at Check-In (Desktop)
Room and tax charges can be posted in three wys: by default, they are automatically posted during the night audit; alternatively, you can post them manually by selecting "Post Room & Tax" from the folio toolbox; and finally, they can be automatically posted at check-in. This last option can be activated in the parameters section.
Path: Management > Setup > Property > Parameters > Section "Parameters" (right side)
Choose "On" next to the parameter "Post Rm & Tax On Checkin".
Posting room and tax at check-in means that you will not be able to use the "Undo Check-In" in a reservation anymore. As soon as something is posted on a reservation folio, even if voided, prevent the check-in to be undone. If a reservation has to be undone, it will only be by checking it out.