Paperwork, paper pushing policies push people past pressure points

So I am going to make this simple here.  Paperwork at UC Davis is driving me batty these days.  One thing in particular does not make much sense to me. When I or anyone who works in my lab go on trips associated with work, we have to collect all the receipts for the trip and then these need to be submitted in an intemized way for reimbursement.  With a lot of people going on a lot of trips, this amounts to a lot of work for us, for my administrative assistant, for the UC Davis Genome Center administration, and for the UC administration.  At other places I have worked, and in other situations, people can get reimbursed using a per diem calculation.  Such calculations save an absurd amount of work for people even if they come with some "risks" such as people getting reimbursed for more than they actually spent.  Personally, I would take a 50% per diem to save everyone the trouble associated with all the reciepts and submitting them and checking them and such.

So - the reason I am writing is to ask - what happens at other institutions?  Does everyone have to submit all the receipts?  Or does anyone out there do per diems?