Our API directory now includes 35 invoicing APIs. The newest is the CashFlows API. The most popular, in terms of mashups, is the PayPal API. We list 33 PayPal mashups. Below you'll find some more stats from the directory, including the entire list of invoicing APIs.
When someone says, "invoicing," do you think: "speed"? Debitoor is designed to get a small business up and running fast--so you can start generating those all-important invoices and get paid faster. The Debitoor API allows a third party app to set up an invoice (such as a point-of-sale app). Debitoor is RESTful API with responses in JSON, according to the API documentation. It joins 48 accounting APIs listed in our API directory.