How
First, you will need to open up the invoice you need to edit. On the right hand side there is a tile that summarizes the payment amount and who was billed. As long as you have the Global Financial authorization, you will see an edit icon that you can press to change the customer invoiced.
Once you click the Edit, type in the new customer who should be invoices and press the Save button.
Once this has been updated, the invoice will be updated as well as the Invoice summary page for both customers.
Audit Log
In case you need to look into changes that have been made on invoices, you can run the Audit Log report. In the global search box, type in "Audit Log". Change the drop down for "View Changes" to "Invoices". From here you can decide if you want to see a specific Invoice history, date range or changes made by a specific user (employee).