You can absolutely copy an existing invoice. On the invoice details page of an existing invoice select “Copy” from the action drop-down.
Figure: Click Copy to Create a Copy of an Invoice
Select the Customer for the new copied invoice and click “Create Copy”.
Figure: Select Customer to Copy Invoice for
This will pre-fill the invoice page with all the information from the existing invoice. Make any changes you wish and click “Save Invoice”.
Learn more about Invoicing with our Getting Started with Invoices Guide.