Probably because of the invoices that get attached to things like Amazon deliveries or shipping loads, that record order details even though paid. I think in my head "invoice", as in "this is a record of the entire transaction, which has been completed when you accept the stuff it's accompanying" is a homonym of "invoice", which means "a request for payment thing".
(no subject)
Date: 2011-03-31 11:49 pm (UTC)(no subject)
Date: 2011-04-01 01:39 am (UTC)