How to chase an invoice that's overdue

Hi [Client name],

Just flagging that invoice [invoice number] for [amount], due [due date], hasn't come through yet. No rush on the explanation. Could you confirm the date it will be paid? I'm happy to resend the invoice or the payment details if that's easier.

Thanks,
[Your name]

Hi [Client name],

I hope things are going well. I noticed that invoice [invoice number], for [amount], is now past its due date of [due date]. These things slip through, so this is a friendly nudge. Could you tell me when payment is likely to land? I'm glad to resend anything you need.

Best,
[Your name]

Hi [Client name],

Invoice [invoice number] for [amount] is now well past its due date of [due date]. Please arrange payment within the next five business days. If there is a reason for the delay that I don't know about, tell me today. Then we can fix it before it becomes a bigger conversation.

[Your name]