Types of digital invoices

Directive 2014/55/EU on electronic invoicing in public procurement uses the term "electronic invoice", and defines it as "an invoice that has been issued, transmitted and received in a structured electronic format which allows for its automatic and electronic processing". In accordance with the Directive, the European standard on eInvoicing specifies invoices in a standardised structured data format that provides for automatic reading of the data into computer systems. The main objective is thus to process the invoice automatically, and human-readable visualisation is secondary.

Specifically, an electronic invoice is a form of a digital invoice. A digital invoice is a document that exists in a digital format as opposed to a physical format (such as a paper invoice), where digital is defined as "composed of data in the form of especially binary digits" (Merriam-Webster). Digital invoices can be transmitted as files through computer messaging networks, but different types of digital documents have different characteristics that affect how they can be processed. There are two main aspects to a digital invoice: the visual aspect and the data aspect. The visual aspect allows a human reader to see the content of a document, and the data aspect allows a computer to process the information contained in the document.

Visual digital formats

In visual formats, the primary aspect is visualisation of the content, which assumes human processing.

• .pdf, digital document format (common in emails) ¹
• .jpg, .png, .gif (common picture formats)
• .tif (common in scanning solutions)

Data formats

In data formats, the primary aspect is computer processing of the data, but some formats may also provide for visualisation.

• Unstructured (The data cannot be automatically read from the document into accounting systems) ²
  • Spreadsheets, word processors etc.
  • HTML  (common in emails and on web sites)
• Structured (The data can be automatically read from the document into computer systems.)
  • Standardised (Data files based on publicly shared specifications EN 16931, UBL, CII, EDIFACT, etc.)
  • Un-standardised (Internal data files whose structure is not following publicly shared specifications)

eInvoices that comply with the European standard on eInvoicing are always in standardised structured data format.

^₁  The Pdf document format is an XML format but it is designed for visual presentation of its content rather than for automatic reading of its data. The data content of pdf files can be extracted, but the process tends to be fragile and dependent on the visual layout of each invoice. Therefore the .pdf is listed as a visual format in the above list.

_²  Data in spreadsheets, HTML and word processor documents can be defined so that it can be automatically read by the receiving computer system. Such a definition makes the data structured and its automated processing is dependent on the specification of the data structure.