Currently it is only possible to send a receipt after a person has bought a product in the store. Under payment/settings/receipts. But it should also be possible to create and send real invoices. (after someone has bought a product, the system should autocreate and send an invoice, which should be found under Payments/all invoices and estimates. Use case: when someone has bought 2 products by mistake, and one transaction is refunded, formally there should also be sent a credit invoice to this customer. Since no invoices are created at all (for all orders in the Store), it is also not possible to send this person a credit invoice.