Invoices are ellectronic documents exchanged between the store, the consumer and the government tax office through a series of webservices.
Invoices are XML documents with data about the purchase, including products, quantities, etc.
For example, this is an invoce: (it is a page in the tax office - don`t worry about the language Portuguese)
This service is directed to Consumers to receive, index and keep those documents and allow him to track its purchases.
Invoices are fed into the system by e-mail, by server pooling at the tax office, by typing a code on the app, by QRcode/barcode reading containing a URL to get purchase...