Your online invoice is displayed 24 hours after the close of each sale in My invoices in the Client Center 
Invoices can be paid in US dollars with all major credit cards, PayPal, US$ check or bank transfers.

In the invoice section, you have direct access to the certificates for that particular invoice. You can print or download the certificate in PDF format.

Purchases made from Paulus Swaen
Invoices and certificates for items purchased from September 2021 until December 2023 can be found here.
Purchases made before July 2021 can be found Here; you can print or download the certificate in PDF format.