I now spend so much time fighting with clients to get paid that I am convinced that many of them make their payment procedures overly complicated intentionally.  I am disappointed to find that I hold this belief and I am not sure when it became cemented.

Clients that pay copies separately months after they pay for the service fee, multiple checks mailed to/from multiple locations, large checks listing hundreds of invoices with multiple errors, offices for the same company with vastly varying payment procedures.  And never an overpayment, not one!  If it isn't intentional then ... well, I will just keep that conclusion to myself.