Since you already sent a friendly follow-up, I’d make the next message more specific rather than just warmer.
I’d include:
- the invoice amount
- the date it was sent
- the due date / payment terms
- the payment link or payment instructions
- one clear question: “Can you confirm when payment will be made?”
Something like:
“Hi [Name], following up on the final invoice for the website redesign, sent on [date] for $2,500. Could you confirm when payment will be made? If there’s an issue with the invoice or launch handoff, please let me know today so I can help resolve it.”
Still polite, but no ambiguity.