How do I reverse an invoice that was paid in error?

Hello there, @Vinn542.

You can delete the payment to unlink it from your invoice and re-open the said transaction to keep your income transactions accurate in QuickBooks Online (QBO). I'll gladly guide you on how to do this.

1. Open your QuickBooks Online (QBO) account.
2. Click on Sales at the left pane, then select All Sales.
3. Locate the payment from the list, then open the transaction.
4. From the Receive Payment window, click on Delete from the More button.
5. A pop-up window will appear that the transaction is linked to others. Hit Yes, to confirm the action.

Once you're ready to record the appropriate invoice payment, you can refer to this article for the complete guide: Record invoice payments in QuickBooks Online.

Also, you can personalize and add specific info to your sales forms in QBO. You may check out this article if you want to learn more about this feature: Customize invoices, estimates, and sales receipts in QuickBooks Online.

Please feel free to leave a comment below if you have other concerns about managing invoices and payment transactions in QBO. I'm always ready to help. Take care, @Vinn542.