I receieved invoices dating back July 2008 from one of my suppliers for unbilled orders I placed with him. The total of all the invoices come to approximately $17,000.00 of which $5000.00 is from 2008 and $15000 is Jan - April 2009. I investigated and found we actually received the products but were not billed for. How far back can my supplier go to search for unbilled orders and bill me with it? Is there a limit to how far back he can go in terms of years? I am under any obligation to pay these 2 1/2 to 3 years old invoices?