I am a subcontractor and have a contract with a vendor listing net 30 terms, however, their invoices show terms to be "Due upon receipt" which is causing a problem between the GC and my company regarding my payment applications and releases. One of my GC's listed several invoices for the month of February but the invoice dates were listing March. The vendor sends an invoice approximately 10 days after equipment is delivered to the job site requesting payment for a full month. When I called the vendor this morning for date clarification, I was informed the invoice date is inconsequential and that the date I should be using is the delivery date. So far, everything I've read contradicts that explanation because our contract states Net 30 which defines as payment would be due 30 days from the invoice date. What date should be used to determine a due date???