I just implemented a late payment fee. It is hefty! I charge $35 initially, then $20 a day for every day after. I was sick and tired of one family "forgetting" to pay me EVERY week. I sent out a group email, insisted they confirm that they read and agreed to it before coming back to daycare, and they all did. The late family took a few days to respond. She thought I was "stern", and didn't understand why I was so upset. I told her that I wasn't being stern, but assertive. It all worked out, and they haven't paid late again.