When scanning documents containing print that goes all the way to the paper edges, like receipts, the glass flatbed has an unscannable area around the border of the glass.

WTF? Why can’t flatbed scanner makers figure out where to put glass and where to put plastic? I think every scanner I have ever used has this problem. Are there exceptions?

So to cope with the problem I try to position the paper away from the edge. Of course the annoying consequence is that the paper is not exactly parallel to the edge of the scanning area. I suppose a better hack is to put a metal ruler against the edge to give receipts an alignment mechanism.