Lessons learned: Don't overlook the amount of the late-payment fee. My debtors are late every month with their payment, and all I get for my troubles is a lousy $15 fee. That's a nice little bump of $180 every year, but it hardly covers the extra time I spend for bookkeeping. Recalculating the totals every month is a hassle. And $15 per month doesn't "incentivize" them to pay on time.

Insist on a late-payment fee of at least $25, but why stop there? Go for $35 to $50, and you'll see a much-improved on-time payment performance.