A good first step is to call and ask when the check was mailed. If it hasn't been sent, ask when the invoice is scheduled for payment. Your goal is to get a commitment to pay. If the customer won't agree to pay by a given date, find out why. Once you get a reason, end the call.
If you can't get a straight answer, consider your cash-flow needs and options. How important is this account to you? Should you write off the loss this time and insist all future purchases be c.o.d.? Should you send a personal letter? Your relationship with the client will guide you.
If all else fails, turn the matter over to an attorney or a collection agency.
Excerpted fromGet Smart: 365 Tips To Boost Your Entrepreneurial IQ