Universal Business Language (UBL) is an open standard for electronic business documents, for example e-invoices. Launched in 2004, it is designed to facilitate the exchange of structured business information between organizations in a standardized and interoperable manner. UBL provides a common framework for various business documents, including invoices, purchase orders, shipping notices, etc.

UBL is based on the Extensible Markup Language (XML), a widely accepted format for structuring and encoding data. XML enables standardized data representation in a hierarchical, structured, and machine-readable form.

The Organization for the Advancement of Structured Information Standards (OASIS) maintains UBL. It has gained global recognition and adoption, making it suitable for cross-border and international business transactions.

All message types in Peppol are based on UBL.