Receipt collection for Cloudflare
Cardboard automates the collection of receipts for payments made through Cardboard, so you don't have to collect the receipts yourself.
Receipt collection with email
Cloudflare sends receipts to a billing email.
All you need to do to automate the receipt collection is to add the Cardboard subscription's receipt collection email address as the billing email in the service.
Some services support multiple cards but only one billing email. In those cases, set the billing email to your general Cardboard email address.