Is there a way to undo a paid invoice?

Hi vik@cjcad.ca,

Welcome to Community. It essential that your invoices are correctly recorded in your books so that you can get back doing what you love. QuickBooks Online is a great program that gives you the ability to simpy track your sales and expenses. I'd be glad to point you in the right direction regarding your overdue invoice.

 
In order to keep the overdue invoice, you'd need to remove the payment attached to that invoice. I'd encourage you to follow these steps to remove the payment applied to the invoice.

1. Click on Sales on the left navigation menu.
2. Select All sales.
3. Click on the payment.
4. Select  More.
5. Click on Delete and then Yes.

This will allow you to keep  the overdue invoice until you receive payment.

Let me know if you have any questions, I'll be happy to help.