Large organizations move slowly. And they watch their money carefully, as they should. If you have submitted an invoice and have not gotten paid, don't panic. If it's only been a couple of weeks, give it time. If you get on the phone or send an email to your client asking about where your money is, it is very unprofessional. This is what you should do -
• Expect that with large companies processing checks takes a minimum of two weeks. Your invoice is in a huge pile of other invoices that they are taking care of, such as their electric bill, etc. And bigger companies don't write checks every day. In fact, many of them do it monthly. And this is a clue as to what your next step is:
• Send a statement at the beginning of the month. Remember that in large companies, things can be overlooked. A statement is a simple letter (yes, you can send it as an email attachment) that is simply a reminder of an invoice that was submitted the previous month. All you have to do is write "Statement" and "invoice of October 13....etc." and send it. If, for some improbable reason, you don't get paid that month, send another statement the next month.
This is how large companies work. I call it "corporate time" - where "right away" means that someone will begin to think about writing a memo about having a meeting next month. The bad news is that is just the way it is. The good news is that you will be paid. Eventually.