My calm reminder for a late payment

I needed to ask about a late payment.

The invoice was two weeks overdue.

I did not want to upset the client.

So I wrote a short, friendly email.

I said: just a gentle reminder about invoice 204.

Then I asked: could you let me know a date?

I also wrote: happy to sort out any issue on our side.

The client replied within an hour.

She said she forgot to pay.

She sent the payment right away.

We kept a good relationship.