The standard invoices show all phases and % Complete values on them. For example, the Phased Invoice template under the Phased & Joint category of invoice templates shows this information. The best way to preview the invoice template is via Global Settings > Invoice Templates or Projects > General > Billing Options. To view the live invoice, go to the Invoices screen and select 'Preview (Change Template)' from the row action menu. The Phased and Joint > Phased Invoice template can work for you. Check the Core Help for details.