PayPal - Invoicing v2

Use the Invoicing API to create, send, and manage invoices. You can also use the API or webhooks to track invoice payments. When you send an invoice to a customer, the invoice moves from draft to payable state. PayPal then emails the customer a link to the invoice on the PayPal website. Customers with a PayPal account can log in and pay the invoice with PayPal. Alternatively, customers can pay as a guest with a debit card or credit card. For more information, see the Invoicing Overview and the Invoicing Integration Guide.