Thanks for joining this conversation, @guavaria.

You can utilize the Statement feature of QuickBooks Online. It allows you and your customers to keep track of their overdue invoices. I'll help you customize it, here's how:

1. On the top menu, click the Plus icon.
2. Under Others, choose Statement.
   
3. For Statement Type, select Balance Forward.
4. Make sure to select Customer Balance Status.
5. Customize the dates for the transactions to be added on the statement.
6. Click Apply.
   
7. Select the specific customers for the recipients.
8. At the bottom, click Print or Preview.
   

That should help you get the information you need, @guavaria. You can snail mail the letter so your customer will be updated. For future reference, I'm adding here the Create and manage statements article.

Let me know how it goes or if you have any follow-up question about statements. I'll be here if you need further assistance.