Glossary

The vocabulary of
e-invoicing.

The terms that come up on every mandate project, defined the way they actually matter when you are building — not from a textbook. 32 of them, and counting.

Standards & specifications

EN 16931: The European standard that defines the semantic model of a core invoice — what each field means, independent of how it is encoded. Two syntaxes (UBL and CII) are compliant with it, and most EU mandates build on it as the reference point.
UBL Universal Business Language: An OASIS XML vocabulary. UBL 2.1 is one of the two syntaxes that can carry an EN 16931 invoice, and the one most Peppol-based mandates use.
CII Cross Industry Invoice: A UN/CEFACT XML syntax and the second EN 16931-compliant option alongside UBL. It is the structured payload embedded inside Factur-X / ZUGFeRD.
CIUS Core Invoice Usage Specification: A compliant narrowing of EN 16931 for a country or context — it can make optional fields mandatory or restrict code lists, but must not contradict the core. Peppol BIS Billing is a CIUS.
Extension: Where a jurisdiction needs data the EN 16931 core cannot express, an extension adds it on top of the core rather than bending the core itself.
PINT Peppol International Invoice: Peppol's global invoice base specification, localised by country profiles (PINT AE, PINT OM, JP PINT). It generalises the European model for worldwide use.
Peppol BIS Billing 3.0: The Business Interoperability Specification for billing on the European Peppol network — a CIUS of EN 16931 together with transport rules.

Networks & transport

Peppol: A network and governance framework for exchanging structured business documents through certified access points, overseen by OpenPeppol and national Peppol Authorities.
Access Point AP: A Peppol-certified service provider that connects a party to the network. In corner terms it is C2 (the sender's) or C3 (the receiver's).
SML Service Metadata Locator: The DNS-based directory that resolves a participant identifier to the address of its SMP.
SMP Service Metadata Publisher: Publishes, per participant, which document types it can receive and the endpoint to deliver them to — the basis for looking up a counterparty's capability before sending.
Participant identifier: How a party is addressed on the network: a scheme code drawn from a controlled list plus a value, such as a VAT or company registration number.

Control models

CTC Continuous Transaction Controls: Any model in which the tax authority collects invoice data at or near the time of the transaction, rather than through a periodic return.
Clearance: A CTC model where the authority validates the invoice and returns an identifier before it is legally valid — the authority sits inside the send path.
Four-corner model: Supplier → sender access point → receiver access point → buyer. The tax authority takes no part in the exchange.
Five-corner model: The four-corner model plus the tax authority as a fifth corner, receiving the invoice or a report derived from it.
E-reporting: Reporting transaction data to the authority — distinct from e-invoicing (exchanging the invoice with the buyer). A regime can require one, the other, or both.
DRR Digital Reporting Requirements: Under ViDA, near-real-time transaction-level reporting of intra-EU B2B supplies, replacing the recapitulative statement from 1 July 2030.
ViDA VAT in the Digital Age: The EU package (Council Directive (EU) 2025/516) reforming VAT for e-invoicing and digital reporting, the platform economy, and single VAT registration — phased from 2025 to 2035.

Formats & national systems

Factur-X / ZUGFeRD: A hybrid invoice: a human-readable PDF/A-3 with structured CII XML embedded inside it. Called Factur-X in France and ZUGFeRD in Germany.
FatturaPA: Italy's national invoice XML, exchanged through the SdI clearance platform. It is a national schema with an Italian usage profile, not native EN 16931.
SdI Sistema di Interscambio: Italy's central clearance platform, which validates and forwards every invoice and returns delivery or rejection receipts.
KSeF Krajowy System e-Faktur: Poland's national e-invoicing system — a clearance model built on the FA(3) structured schema.
SAF-T Standard Audit File for Tax: An OECD-derived XML file of accounting and transaction data submitted periodically or on demand — a reporting obligation, not invoice exchange.
IRN / IRP India: India's Invoice Registration Portal (IRP) issues an Invoice Reference Number (IRN); for a notified taxpayer, an invoice without a valid IRN is not a valid tax invoice.

Validation

XSD XML Schema: Validates the structure of an XML document — elements, data types and cardinality. Necessary, but nowhere near sufficient for compliance.
Schematron: A rule language for the business rules an XSD cannot express — cross-field checks, conditional requirements, code-list membership. Where most real validation failures surface.
Code list: A controlled set of allowed values — currencies, tax categories, unit and country codes. Often versioned separately from the rules, and a frequent, quiet cause of rejection.

Document & scope concepts

Self-billing: The customer issues the invoice on the supplier's behalf under an agreement — a distinct document type most mandates handle explicitly.
Credit note: A document that reduces or reverses a previous invoice. Under clearance you correct with one rather than deleting the original, which no longer exists to delete.
B2B / B2G / B2C: Business-to-business, -government and -consumer transactions. Mandate scope is usually sliced by these categories, and the rules differ per type.
BT / BG Business Term / Business Group: EN 16931's identifiers for data elements (e.g. BT-25, "Preceding invoice reference") and their groupings (BG-). The shared vocabulary for format mapping.

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The vocabulary ofe-invoicing.