The single most common piece of lost revenue in a small hotel with a restaurant is the charge that never made it onto the room bill. Someone wrote it on a docket, the docket went missing, the guest checked out.
When the till and the front desk share a billing anchor, the transfer is a posting rather than a hand-off. The outlet bill is settled by a cash-equivalent tender and one aggregated line lands on the stay folio — correctly taxed at the outlet, so the guest is never taxed twice.
The reverse direction matters as much. Because the outlet folio remains linked, checkout can refuse to complete while an outlet bill against that room is still open and unpaid, and it will name which one.
Stock moves in the same transaction as the sale, drawn FIFO from the batch it was actually received in, so food cost is measured rather than estimated. And the drawer that took the cash reconciles on its own terms at shift end.