Hi userdonnanicks,
Welcome to the QuickBooks Community forum! In here you can find answers to a ton of questions and post your own for others to answer. I'd be happy to help you with this and get you back to business.
In QuickBooks Online one of the greatest features is that you can modify the information you put in because lets be honest, accidents happen. In order to change customer information on an invoice you can edit the invoice by going to Sales>Invoices>Select Invoice to change>Click Edit Invoice. Once you're in the invoice you can change the client from the top drop down menu under customer.
If you meant you entered it into the wrong clients company account then you can import the invoices into the correct company but you'll need a third party app to export the invoices into a .CSV file. You can find one by clicking on Apps on the left hand side of the screen. Once you find an one to help you export the files you can import them by following the steps in this article.
Should you have any further questions please feel free to reach out to us and we would be happy to help!
