First polite reminder
Hi [Name], quick reminder that invoice [Number] for [Amount] was due on [Date]. Could you confirm when payment will be processed? Thank you.
Second reminder
Hi [Name], following up again on invoice [Number]. It is currently overdue, and I wanted to check whether anything else is needed from my side to process payment.
Final reminder
Hi [Name], I am following up one final time on invoice [Number] for [Amount]. Please confirm the payment timeline or let me know who I should contact to resolve this.
Track every reminder
Save the stage, send date, message used, response, and next follow-up date. That gives you a clear history instead of guessing what happened.