I marked off an invoice as paid by mistake

Not to worry, Leon. I'm here to help you handle these invoices in QuickBooks Online.

You can delete the corresponding payment entry of these invoices. Then, you can make any edition to the invoice afterward. Here's how:

1. Go to Sales and select Invoices.
   
   
    
2. Open the specific invoice, and on the invoice entry screen at the top right corner, click on the 1 payment link.
3. On the payment entry screen, choose More and click Delete. You have two options: edit the payment entry to show the correct invoice paid or delete it.
   
   

I'm adding these articles you can use in the future:

• Record invoice payments in QuickBooks Online.
• Take and process payments in QuickBooks Online with QuickBooks Payments.

By following these steps, you can reinstate your invoices in QuickBooks Online. If you have more questions about managing your invoices, post them here in the forum again or comment on them below. I'll be just around the corner. Stay safe!