Thank you for reaching out to the QuickBooks Community. I can help you undo a transaction if your invoice was mistakenly marked as paid in QuickBooks Online (QBO).
We can unlink or delete the payment transaction to have the invoice tagged as Open again. Then, you can create a new receive payment and link it to the correct invoice. Here are the steps:
- Go to the Sales menu.
- Select the All Sales section.
- Locate and click the payment transaction.
- You'll be routed in the Received Payment page.
- Tap More at the bottom and choose Delete.
- You'll be prompted with Are you sure you want to delete this? Hit Yes.
After that, let's create and send the corrected invoice:
- Go to + New and select Invoice.
- Select a customer from the Customer drop-down.
- Fill out the necessary information for Service Date, Product/Service, Qty, Rate, and Amount.
- Click Save and close.
See this article for other ways of correcting payments: How to fix a payment applied to the wrong customer invoice.
In addition, I'm leaving you this article if you'd be interested in personalizing your sales forms: Customize invoices, estimates, and sales receipts in QuickBooks Online. It will help you enhance the appearance and layout of your invoice, so it'll look pleasing and professional to your customers.
That will automatically change the status of the invoice to Open (or unpaid). Don't hesitate to add a comment if you have follow up questions.
