Glossary
Addenda
An addenda is the optional node of a CFDI, Mexico's electronic invoice, that holds extensions to the SAT format useful to the taxpayer, that is, information the Annex 20 standard does not provide for.
The Annex 20 schema defines it as an optional node to receive extensions to the format that are useful to the taxpayer, and refers its rules of use to the originating format. The SAT’s CFDI 4.0 filling guide, accessed October 17, 2026, gives an example: because Annex 20 is a predefined, closed technical standard, CFDI issued under public works or real estate contracts can include the penalties or breaches of those contracts in the addenda.
What sets it apart from a complement is who decides its content. Complements are set by the SAT, Mexico’s tax administration, for a specific sector or activity, like the Carta Porte, and the digital tax stamp (Timbre Fiscal Digital) is always included; the addenda carries whatever is useful to the taxpayer.
In Odoo 20, addendas are configured as nodes in the Addendas & Complementos (MX) menu and assigned to a contact, so they go on all of its invoices, or to a single invoice; Odoo’s documentation warns that this setup may require technical knowledge, as the Mexican localization guide details.
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