large rental company invoice tracking

[RobertLangdon]

hello, we just started doing business with a large rental company. They are buying anywhere from 7,000 to 10,000 a week! The deal states it is my resposibility to track all invoices. They give me a PO and a Unit number. If any one has experience with a rental company (hertz, avis, enterprise) How do you track there invoices and any other advice to keep them happy. They have aprox. 12 different location to deliver to. Any advice would be great.