Electronic invoicing (also called e-invoicing or einvoicing) is a form of electronic billing. E-invoicing includes a number of different technologies and entry options and is usually used as an umbrella term to describe any method by which a document is electronically presented from one party to another, either for payment or to present and monitor transactional documents between trade partners to ensure the terms of their trading agreements are being met. These documents can include invoices, purchase orders, debit notes, credit notes, payment terms, payment instructions, and remittance slips.

A business's accounts payable department ensures that all invoices from its suppliers are approved, processed, and paid. The main responsibility of the accounts receivable department is to ensure all invoices are created, delivered and subsequently paid by their customers. Processing an invoice includes recording relevant data from the invoice and feeding it into the company's financial or bookkeeping systems. After the feed is accomplished, the invoices go through the company's business process to be paid.

An e-invoice can be defined as structured invoice data issued in electronic data interchange (EDI) or XML formats, possibly using Internet-based web forms. These documents can be exchanged in a number of ways, including as EDI, XML, or CSV files. The company may use imaging software to capture data from PDF or paper invoices and input it into their invoicing system. Many companies hire a third-party company to implement and support e-invoicing processes and to archive the data on their own servers.

The file extension .INV could be used. The .INV file can be in standards-compliant XML format.

Since the mid-1960s, companies have begun establishing data links with trading partners to transfer documents such as invoices and purchase orders. Inspired by paperless office, they developed the first EDI systems. At the time, there was no standard for electronic data interchange.

The Accredited Standards Committee X12, a standards institution under the umbrella of ANSI, moved to standardize EDI processes. The result is known today as the ANSI X12 EDI standard. This remained the main way to exchange transactional data between trading partners until the 1990s, when companies began competing. New web-based applications allow for online submission of individual invoices as well as EDI file uploads, including in CSV, PDF, and XML formats. Suppliers could also see a history of all the invoices they submitted to their customers without having direct access to the customers' systems. This is because all the transactional information is stored in the data centers of the third-party company that provides the invoicing web app.

According to a 2012 Global E-Invoicing Study, 73% of respondents used electronic invoicing to some degree in 2012, a 14% increase from 2011. Supplier resistance to e-invoicing has decreased from 46% in 2011 to 26% in 2012. By 2022, a leading provider reported a 78% increase in the number of invoices processed through its platform over a two-year period. According to a report done by the GXS in 2013, Europe is adopting government legislation encouraging businesses to adopt electronic invoicing practices. The United States Treasury estimated that implementing e-invoicing across the entire federal government would reduce costs by 50% and save $450 million annually.

Various standards exist: the EU's Directive 2014/55/EU on electronic invoicing in public procurement noted that "several global, national, regional and proprietary standards exist; ... none of them prevail and most of them are not interoperable with one another. The number of different standards coexisting across Member States is increasing and is likely to continue increasing in the future". The Directive also noted that