First question are they commercial or personal photography clients?

With commercial clients we ask for a credit card number that we put through in 45 days if a check has not been received. At that point most have a commercial credit card and give permission to use the card when the order is complete, (they like the accumulation of points)

With personal photography if they are not paying in full at the order appointment, they leave me two credit card #s with signed authorization to put the amount through in up to 4 spaced out payments. (make it a new accounting procedure). If you do not take payments by credit cards get post dated checks.