Statement mailed with finance charges attached. Phone calls to accounts payable to ask where payment is. Phone calls to your contact making sure everything was delivered and acceptable - you're just trying to determine why payment has been delayed.<p>Personally, the phone call to accounts payable usually works. If not, the phone call to your client contact usually gets it resolved.<p>Refusal to do more work until past invoices are paid or mentioning that you've got to postpone development on their project for other paying clients (this can backfire).<p>We also have an automated system that sends out reminders - our response is usually, yes that is an automated process, but, while you're on the phone....