You can get an invoice from the reseller: 2checkout or Verifone. (You will not get an invoice from Exoside because, you have bought QuadRemesher to the reseller (2checkout or Verifone), not to Exoside.) For this purpose, you will have to click on the "Signup / Login" link that is at the bottom of the email you have received from the reseller (2checkout / Verifone). (This email is the one in which you received your License Keys) Once logged on 2checkout/Verifone's web site, you will be able to ask for a invoice.