Reminder 1 — the polite nudge (+3 days)
Subject: 'Invoice 2026-014 — quick check'. Body: 'Hi Sam, hope the launch went well. Invoice 2026-014 ($1,840, due 12 Sep) looks like it hasn't been paid yet — could be on your side. Could you confirm it's scheduled? Copy attached. Thanks!' Friendly, zero blame, one question.
Reminder 2 — the firmer follow-up (+10 days)
Subject: 'Invoice 2026-014 — overdue 10 days'. Body: 'Hi Sam, invoice 2026-014 is now 10 days past its due date. Please arrange payment this week or let me know the exact date it will be released. Re-attached for your records.' Now there is an explicit ask and a deadline.
Reminder 3 — the final notice (+20 days)
Subject: 'Invoice 2026-014 — final notice'. Body: 'Hi Sam, despite two reminders, invoice 2026-014 ($1,840) remains unpaid 20 days after its due date. Please pay by [date] or reply with a payment plan proposal. After that date I'll pass the debt to collections / pause further work.' Say what you will do — then do it.
Rules that keep you paid and professional
- Never renumber — every reminder references the original invoice number
- Attach the invoice again every time (they lost it, every time)
- Keep it factual: dates, amounts, one clear ask
- Escalate on a schedule, not on emotion
- For retainers, pause work at final notice — it gets answered