Why say "due June 15" instead of "Net 30"?
A specific date removes any ambiguity about when the clock started — "Net 30" requires the client to do math and assume they got the invoice on the right day.
Is a late fee clause actually worth adding?
It often speeds up payment even when it's never enforced — just having it stated up front signals that payment terms are taken seriously.
What's the right tone for a first overdue reminder?
Friendly and assuming good faith — "just following up in case this got missed" — most late payments are genuinely accidental, not a refusal to pay.
When should I stop working for a client who isn't paying?
That's a business judgment call, but pausing further work until an invoice is settled is a completely reasonable last resort once reminders and a direct call haven't worked.