An e-invoice is an electronic version of traditional paper-based invoices. It is a document created, stored and transmitted in digital formats to keep a record of sales transactions and payments for services. E-invoices are sent and received electronically between businesses or between businesses and their customers, usually by email or through specialized e-invoicing service providers.

E-invoices are used to reduce paper waste, lower transaction costs and speed up transaction processes. They also offer advantages such as easier tracking of records and automation of accounting processes. In terms of security and compliance, e-invoices must generally comply with certain standards and regulations and are often secured with digital signatures or other security measures.