First, my apologies - this is probably a very obvious/silly question for most of you! Secondly, sorry for hijacking the thread but I felt this was a related voucher topic.

If you stay at a hotel on a prepaid rate (and of course pay upfront) can you use a voucher to pay for incidentals (e.g. meals, mini-bar) for that stay?

If yes to the above, do you need to provide the hotel with a voucher a check-in or can you do so at a later time (i.e. when you know what the value of incidentals will be)?