How do you get a large company to expedite payment?

first of all you have to ensure that all the necessary documents related to the payment are submitted . most of the large companies are process driven which forces to have automated systems . after submitting your invoice as well as supporting documents , you need to ensure that your invoice has been entered in the automated system and you have been provided with some refernce number for tracking the progress this will help you to provide clarifications to persons raising concerns and expedite the clearance process from their respective workflow