E-Invoicing Glossary

Plain-language definitions for developers and finance teams

53 terms in 13 categories

Electronic invoicing is reshaping how businesses and public authorities exchange financial documents across Germany and the EU. Whether you are a developer integrating XRechnung into an ERP system, a finance manager preparing for the B2B e-invoicing mandate, or a public-sector buyer receiving invoices via ZRE or OZG-RE — understanding the underlying standards, data structures, and legal framework is essential.

This glossary covers 53 key terms spanning the full e-invoicing landscape: the major formats (XRechnung, ZUGFeRD, Factur-X), the foundational European norm (EN 16931) with its Business Terms and Business Groups, transmission infrastructure (Peppol, ZRE, OZG-RE), XML technologies (UBL, CII, Schematron, XSD, XSLT), VAT concepts (reverse charge, intra-community supply, small-business rule), German tax law (GoBD, retention obligations, Wachstumschancengesetz), and payment data standards (IBAN, BIC, SEPA direct debit).

All definitions are available in both German and English. Terms are grouped by category below. Click any term to read its full definition and discover related concepts via cross-links.

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Authority— 1 term

KoSIT (Coordination Office for IT Standards)

The Coordination Office for IT Standards (KoSIT) is an institution of the Free Hanseatic City of Bremen that develops and maintains IT standards for public administration on behalf of the IT Planning Council of Federal and State Governments. KoSIT is responsible, among other things, for maintaining the XRechnung standard, the open-source Validator tool, and operating the national Peppol infrastructure in Germany.

Business Group (BG)

A Business Group (BG) groups semantically related Business Terms (BT) of the EN 16931 standard into a logical unit. Examples include BG-4 (Seller), BG-7 (Buyer), or BG-23 (VAT breakdown). Business Groups can be nested and provide a structured organisation of the invoice data model.

Business Term (BT)

A Business Term (BT) is a single, semantically defined data element of the European standard EN 16931. Each Business Term has a unique number (e.g., BT-1 for the invoice number, BT-9 for the payment due date), a name, a definition, and cardinality rules. Business Terms are syntax-independent and are mapped to different XML elements in UBL and CII.

Buyer Reference (BT-10)

The Buyer Reference (BT-10) is an identifier specified by the buyer for internal routing and assignment of the invoice at the recipient's end. In the German B2G sector, this field is mandatory for XRechnung and is populated with the Leitweg-ID. For B2B invoices, BT-10 often serves as an order reference or cost-centre identifier and enables automated invoice processing.

Credit Note / Corrected Invoice

A credit note or corrected invoice is issued when an original invoice was erroneous or a supply is reversed. In EN 16931, a credit note is identified with invoice type code 381 and a corrected invoice with code 384. The corrective invoice typically contains the original invoice number as a reference (BT-25) and must include all mandatory fields just like a regular invoice.

Invoice Attachment (BG-24)

Business Group BG-24 (ADDITIONAL SUPPORTING DOCUMENTS) allows embedding or referencing attachments in an electronic invoice. Attachments can be embedded directly in the XML file as Base64-encoded binary data or referenced via a URI. Typical attachments include delivery notes, proof of service, or order confirmations. Maximum file size and permitted file types are implementation-dependent.

Invoice Number (BT-1)

The invoice number (BT-1) is a unique alphanumeric identifier assigned by the seller to an invoice. It is a mandatory field under EN 16931 and must be unique within the seller's invoicing period. The invoice number is tax-relevant (§ 14 para. 4 UStG) and is used for referencing on payment documents and in communication with the buyer.

Invoice Type Code (BT-3)

The Invoice Type Code (BT-3) specifies the type of document represented by an electronic invoice. It is based on the UNTDID code list 1001. Commonly used codes include 380 (Commercial invoice), 381 (Credit note), 384 (Corrected invoice), and 389 (Self-billed invoice). Correct specification is mandatory under EN 16931.

Order Reference (BT-13 / BT-14)

BT-13 (buyer's order identifier) and BT-14 (seller's order identifier) allow linking an invoice to a purchase order. In public procurement, providing the order reference is often obligatory to enable automated three-way matching (order, goods receipt, invoice). Both fields are optional under EN 16931 but may be defined as mandatory by public buyers.

Payment Terms

Payment terms specify the period and conditions under which an invoice must be settled. In electronic invoices under EN 16931, payment terms are structured in BG-16 (Payment instructions), including the due date (BT-9), payment means (BT-81), discount/early payment terms (BG-29), and payment reference (BT-83). Clear payment terms are important for automated processing and timely payment.

Self-Billing

In self-billing, the buyer (recipient) issues the invoice on behalf of the seller (supplier). This procedure is governed by § 14 para. 2 UStG and requires an explicit agreement between the parties. On electronic invoices, self-billing is indicated by invoice type code 389 (BT-3). It is common in the automotive industry and in complex supply chains.

Semantic Data Model

The semantic data model of EN 16931 describes the meaning-based structure of an electronic core invoice independent of concrete XML syntaxes. It defines all Business Terms (BT) and Business Groups (BG) with their precise meaning, cardinality, and permitted values. Through syntax independence, the same substantive information can be expressed in both UBL and CII.

VAT Category Code (BT-151)

The VAT Category Code (BT-151) classifies the type of VAT applied to an invoice line. The permitted values come from UNTDID code list 5305 and include S (Standard rate), Z (Zero rate), E (Exempt), AE (Reverse charge), K (Intra-community supply), G (Export), and O (Outside scope of VAT). Correct usage is essential for tax compliance.

E-Invoice

An e-invoice in the strict sense is an invoice that is issued and received in a structured, machine-readable format and enables automatic electronic processing. In the German context, particularly following the Growth Opportunities Act, e-invoice explicitly refers to structured formats (XRechnung, ZUGFeRD/Factur-X, Peppol BIS), while pure PDF invoices no longer qualify. Hybrid formats such as ZUGFeRD count as e-invoices because they contain the XML structured data.

Incoming Invoice

An incoming invoice is an invoice that a company or authority receives from a supplier. In the context of electronic invoicing, from 2025 the invoice recipient is required to be able to receive structured electronic invoices. Proper verification, account assignment, and GoBD-compliant archiving of incoming invoices is a prerequisite for input VAT deduction.

Leitweg-ID

The Leitweg-ID is a unique routing identifier used by German public sector buyers to receive electronic invoices. It typically consists of a combination of an authority code, optional subdivisions, and a check digit, e.g. `991-12345678-06`. The Leitweg-ID is provided in the XRechnung field BT-10 (Buyer Reference) and ensures that an invoice is correctly delivered and processed within an authority.

Outgoing Invoice

An outgoing invoice is an invoice that a company issues to a customer. From certain transitional deadlines (depending on company size, by 2028 at the latest), domestic outgoing invoices in the B2B sector in Germany must be issued as structured e-invoices. For B2G outgoing invoices to federal authorities, this obligation has applied since 2020.

Peppol

Peppol (Pan-European Public Procurement On-Line) is an international network and infrastructure for the secure electronic exchange of business documents, especially invoices and orders. It is based on a four-corner model with Access Points, a central directory (SMP/SML), and standardised document formats (e.g., Peppol BIS Billing 3.0 based on UBL). In Germany, KoSIT operates the Peppol directory.

Peppol Access Point

A Peppol Access Point is a certified service provider that acts as an entry and exit point for the Peppol document exchange. Businesses and authorities can send and receive invoices through an Access Point without being directly connected to the Peppol network. Access Points must be certified by Peppol authorities (in Europe, OpenPeppol) and commit to complying with Peppol interoperability specifications.

B2B (Business-to-Business)

B2B refers to business relationships and invoicing between two companies. In Germany, the Growth Opportunities Act (2024) introduced a mandatory electronic invoicing obligation for domestic B2B transactions as well. From 2025, businesses must be capable of receiving e-invoices; the obligation to issue them will be phased in until 2028. ZUGFeRD and XRechnung are both permitted formats for B2B.

B2G (Business-to-Government)

B2G refers to business relationships and invoicing from companies to government entities (federal, state, municipal, and public bodies). In Germany, electronic invoicing in the B2G sector has been progressively mandatory for federal authorities since 2020 and increasingly for state and municipal authorities. The required format is XRechnung or another EN 16931-compliant format.

FeRD (Forum for Electronic Invoicing Germany)

The Forum for Electronic Invoicing Germany (FeRD) is a multi-stakeholder body comprising associations, software vendors, and authorities. It developed the ZUGFeRD standard and jointly maintains it with the French FNFE-MPE as Factur-X. FeRD promotes the adoption of structured electronic invoices in Germany and publishes the official ZUGFeRD specifications.

BIC (Bank Identifier Code)

The BIC (Bank Identifier Code), also known as the SWIFT code, is an international bank identification code (ISO 9362) that uniquely identifies a bank or financial institution worldwide. It consists of 8 or 11 characters. On electronic invoices, the BIC can be provided in BT-86. Within the SEPA area, the BIC has not been mandatory for private individuals making IBAN transfers since 2016.

IBAN (International Bank Account Number)

The IBAN (International Bank Account Number) is an internationally standardised account number (ISO 13616) that combines a sort code and account number in a uniform format. In Germany, the IBAN consists of 22 characters (DE + 2 check digits + 18-character BBAN). On electronic invoices, the payee's IBAN is specified in BT-84 when bank transfer is selected as the payment method.

SEPA Direct Debit

The SEPA direct debit scheme allows creditors to collect amounts directly from the debtor's account with their consent (mandate). On electronic invoices, SEPA direct debit can be specified as the payment means (BT-81, code 49); the mandate reference (BT-89) and creditor identifier (BT-90) are required. The scheme simplifies recurring payments and accelerates payment receipt.

Invoice Receipt Platform

An invoice receipt platform is a digital system through which companies and public bodies receive, validate, and further process electronic invoices. In Germany, ZRE and OZG-RE are the primary platforms for the public sector. Platforms check incoming invoices for compliance with the XRechnung standard and route them to the responsible unit within the authority.

OZG-RE (OZG-compliant Invoice Receipt Platform of the Federal States)

OZG-RE stands for OZG-compliant invoice receipt platform and refers to a unified solution for receiving electronic invoices for federal and state authorities and municipalities that do not operate their own ZRE. It is used for invoices addressed to indirect federal administration bodies as well as many state and municipal administrations, and is closely linked to the Online Access Act (OZG).

ZRE (Central Invoice Receipt Platform of the Federal Government)

The Zentrale Rechnungseingangsplattform (ZRE) is the official receipt platform for electronic invoices addressed to direct federal government authorities in Germany. Invoices can be submitted via the ZRE through a web form or via established transmission channels (Peppol, email, De-Mail, web service). It is operated by Bundesdruckerei.

EN 16931

EN 16931 is the European standard that defines the semantic data model of a core invoice. It specifies the mandatory and optional fields (Business Terms), their meaning, and the validation rules that apply to all conforming electronic invoices in the EU. Nationally implemented standards such as XRechnung, ZUGFeRD (EN 16931 profile), and Factur-X must comply with this standard.

Factur-X

Factur-X is the Franco-German standard for hybrid electronic invoices, jointly developed by the French association FNFE-MPE and the German FeRD. Technically, Factur-X is identical to ZUGFeRD from version 2.0 onwards and uses UN/CEFACT CII as its XML syntax. The format is recognised across the European Union as a de facto standard for hybrid B2B invoices.

PDF/A-3

PDF/A-3 is an ISO standard (ISO 19005-3) for long-term archiving of PDF documents that, unlike earlier variants (PDF/A-1, PDF/A-2), allows embedding of arbitrary file types as attachments. ZUGFeRD and Factur-X exploit this capability to embed the XML invoice data inside the PDF file, making the document simultaneously human-readable and machine-processable.

Peppol BIS Billing 3.0

Peppol BIS Billing 3.0 (Business Interoperability Specification) is the Peppol specification for EN 16931-compliant invoices based on UBL 2.1. It defines the permitted content, mandatory fields, and code lists for invoices exchanged over the Peppol network. BIS Billing 3.0 is the standard for public procurement in many EU countries and is interoperable with XRechnung.

XRechnung

XRechnung is the German standard for structured electronic invoices in public sector procurement (B2G). It is based on the European standard EN 16931 and is available in two syntaxes: UBL 2.1 and UN/CEFACT CII. Since 27 November 2020, federal public buyers have been required to accept electronic invoices in XRechnung format, and state and municipal authorities have been progressively included.

ZUGFeRD

ZUGFeRD (Zentraler User Guide des Forums elektronische Rechnung Deutschland) is a hybrid invoice format that combines a human-readable PDF/A-3 file with embedded machine-readable XML data. The format is maintained by the Forum elektronische Rechnung Deutschland (FeRD) and exists in several profiles (MINIMUM, BASIC, EN 16931, EXTENDED). It is technically identical to the European Factur-X standard.

ZUGFeRD Profile

ZUGFeRD defines several conformity profiles with different functional scope: MINIMUM (basic data only, not tax-complete), BASIC WL (document data without line items), BASIC, EN 16931 (fully EN 16931-compliant), and EXTENDED (with additional national extensions). For processing by public bodies in Germany, at least the EN 16931 profile is required.

CII (UN/CEFACT Cross Industry Invoice)

CII stands for Cross Industry Invoice and is the UN/CEFACT XML document format for invoices. It is one of the two syntaxes permitted by EN 16931 alongside UBL and forms the basis of ZUGFeRD and Factur-X. CII documents use the namespace `urn:un:unece:uncefact:data:standard:CrossIndustryInvoice:100`.

UBL (Universal Business Language)

UBL (Universal Business Language) is an OASIS-standardised XML vocabulary for business documents, including invoices, orders, and delivery notes. UBL 2.1 is one of the two permitted syntaxes for EN 16931-compliant invoices and is used for XRechnung as well as Peppol BIS Billing 3.0, among others. UBL invoices use the namespace `urn:oasis:names:specification:ubl:schema:xsd:Invoice-2`.

Document Retention Obligation

The statutory retention obligation requires companies to retain invoices and other tax-relevant documents for a period of 10 years (§ 147 AO). Electronic invoices must be archived in their original electronic form — retention solely as a printout is insufficient. The GoBD specify the technical and organisational requirements for audit-compliant archiving.

GoBD (Principles for the Proper Keeping and Storage of Books, Records and Documents in Electronic Form)

The GoBD are administrative guidelines issued by the German Federal Ministry of Finance for audit-compliant archiving and retention of tax-relevant documents in electronic form. They set requirements for immutability, completeness, orderliness, traceability, and machine readability. Electronic invoices must be retained in compliance with GoBD requirements — i.e., in their original electronic format, not as printouts.

Growth Opportunities Act

The Growth Opportunities Act (officially: Gesetz zur Stärkung von Wachstumschancen, Investitionen und Innovation sowie Steuervereinfachung und Steuerfairness) was passed in March 2024 and regulates, among other things, the phased introduction of mandatory electronic invoicing in the B2B sector in Germany. From 2025, all domestic B2B invoices must be issued in a structured format and businesses must be capable of receiving them; transitional exemptions apply on a staggered basis until 2028.

Input VAT

Input VAT refers to the value added tax a business pays on purchases of goods and services, which it can deduct from its own VAT liability to the tax authority (input tax deduction). A prerequisite for the input tax deduction is a proper invoice (§ 14 UStG), which for electronic invoices means correct compliance with all mandatory fields under EN 16931.

Intra-Community Supply

An intra-community supply is the delivery of goods from one EU member state to another where both the supplier and the acquirer are VAT-registered. The supply is tax-exempt in the country of origin (§ 4 No. 1b UStG) and subject to acquisition tax in the destination country. On electronic invoices, VAT category code K (BT-151) is used.

Reverse Charge

Under the reverse charge mechanism, the VAT liability is shifted from the supplier to the recipient of the supply. In Germany it applies to, among other things, certain construction services, metal supplies, and all cross-border B2B services within the EU. On electronic invoices, the VAT category code AE (BT-151) must be used, and a reference to the legal basis (e.g., § 13b UStG) should appear in the invoice text.

Small Business Rule (§ 19 UStG)

The small business rule under § 19 UStG exempts businesses with annual turnover below a threshold (since 2025: €25,000 in the previous year and an expected €100,000 in the current year) from charging VAT. Small businesses issue invoices without VAT but are also not entitled to deduct input tax. On electronic invoices, the VAT category code E (exempt) must be used.

Tax Number (Steuernummer)

The Steuernummer is an identifier assigned by German tax authorities to individuals and legal entities within Germany. It is state-specific and consists of 10 to 13 digits. On electronic invoices, the seller's Steuernummer can be provided in BT-32 (instead of or in addition to the VAT ID). Unlike the VAT ID, the Steuernummer is not valid EU-wide.

VAT (Value Added Tax)

VAT (Value Added Tax), known in German as Umsatzsteuer (USt) or Mehrwertsteuer (MwSt), is a consumption tax on supplies of goods and services. In Germany the standard rate is 19% and the reduced rate is 7%. Electronic invoices under EN 16931 must state the VAT amount (BT-110), tax rate (BT-152), and taxable base amount (BT-116) for each tax breakdown.

VAT Identification Number (VAT ID)

The VAT Identification Number (VAT ID) is an EU-wide unique identifier for VAT-registered businesses. In Germany it begins with the country code 'DE' followed by 9 digits (e.g., DE123456789). On electronic invoices, the seller's VAT ID is stated in BT-31 and the buyer's in BT-48. It is essential for evidencing cross-border tax-exempt supplies.

Electronic Signature

An electronic signature is used to authenticate and ensure the integrity of electronic documents. In the e-invoicing context, the qualified electronic signature (QES) under eIDAS was one method of ensuring invoice authenticity prior to the introduction of EN 16931. Today, for XRechnung and ZUGFeRD, the inherent structural integrity is considered sufficient; a signature is not mandatory but remains permissible.

Schematron

Schematron is a rule-based validation language for XML documents, based on XPath expressions. In the context of XRechnung and EN 16931, Schematron rules are used to perform content-level plausibility checks that go beyond pure schema validation (XSD). The official Schematron rules for XRechnung are maintained by KoSIT and are part of the open-source Validator.

XPath

XPath (XML Path Language) is a query language for XML documents that enables addressing nodes and values in an XML tree. In the e-invoicing context, XPath is used in Schematron rules to specifically address individual fields of an invoice (e.g., BT-1 or BT-9) and check their content against business rules. Developers also use XPath in XSLT transformations for rendering e-invoices.

XSD Schema (XML Schema Definition)

An XSD schema (XML Schema Definition) defines the formal structure, element names, and data types of an XML document. In the context of XRechnung and EN 16931, XSD schema validation is used as the first validation step to verify that an XML document complies with the basic syntactic structure. Content-level checking of business rules is then performed by Schematron.

XSLT (Extensible Stylesheet Language Transformations)

XSLT is a declarative programming language for transforming XML documents into other formats such as HTML, PDF, or other XML structures. In the e-invoicing domain, XSLT stylesheets are used to convert XRechnung or ZUGFeRD XML files into human-readable HTML or PDF representations. KoSIT provides official XSLT stylesheets for visualising XRechnung documents.

XRechnung Validator (KoSIT)

The XRechnung Validator is a command-line tool developed by KoSIT and released as open source for checking XRechnung documents for conformity. It validates both XML schema validity (XSD) and content-level business rules via Schematron. The tool is regularly updated when new XRechnung versions are released and serves as the reference implementation for validation.

Missing a term? This glossary is continuously expanded. All definitions follow the official specifications published by KoSIT, FeRD, the European Commission, and the German Federal Ministry of Finance.