If you want to change the invoice recipient, you need to open the invoice first. To do that, simply click on "Invoicing" -> "Invoices" and find the one you would like to change.
Set another client as the recipient on the invoice
Open the invoice and click on the "Edit" button in the upper right corner of "Invoice data" section.
You will now see a window where you are able to change invoice data. Note that in order to replace the invoice recipient, this customer needs to be in Insly's system. Simply go to "Customers" tab and click on the "+" sign to add a new customer if the they are not in Insly's database yet.
Next steps are very easy:
Click on "Choose customer".
Find the customer that you want to make the payer for this invoice.
Update the invoice
Before the changes will show on the invoice, you need to update the invoice pdf file. This is done by clicking on "Update invoice" in the upper right corner on the invoice page. Now, when you open the pdf file of the invoice, you will see a new customer as a recipient.