E-Invoicing Knowledge Base
15 guidesWhat is Peppol?
Peppol (Pan-European Public Procurement Online) is the dominant e-invoicing network in Europe. It’s a set of open specifications that define how businesses exchange electronic documents — invoices, credit notes, purchase orders — across borders, systems, and formats. Think of it as SMTP for invoices. Your ERP connects to a certified Access Point. The Access Point routes your invoice to the receiver’s Access Point. Both sides speak the same language (Peppol BIS Billing 3.0), regardless of what ERP, accounting system, or country either party operates in. Originally an EU-funded project launched in 2008 for public procurement, Peppol now covers B2B e-invoicing across 39+ countries with 300,000+ registered participants. As of 2026, Belgium, Germany, and Poland mandate Peppol for B2B transactions. France, Spain, and others are adding Peppol support alongside national systems.
Read guideStandards & Networks
Peppol
Peppol (Pan-European Public Procurement Online) is the dominant e-invoicing network in Europe. It’s a set of open specifications that define how businesses exchange electronic documents — invoices, credit notes, purchase orders — across borders, systems, and formats. Think of it as SMTP for invoices. Your ERP connects to a certified Access Point. The Access Point routes your invoice to the receiver’s Access Point. Both sides speak the same language (Peppol BIS Billing 3.0), regardless of what ERP, accounting system, or country either party operates in. Originally an EU-funded project launched in 2008 for public procurement, Peppol now covers B2B e-invoicing across 39+ countries with 300,000+ registered participants. As of 2026, Belgium, Germany, and Poland mandate Peppol for B2B transactions. France, Spain, and others are adding Peppol support alongside national systems.
EN 16931
EN 16931 is the European standard defining the semantic data model for electronic invoices, published by CEN and mandated by EU Directive 2014/55/EU.
E-Invoicing
E-invoicing (electronic invoicing) is the exchange of invoice documents between supplier and buyer in a structured electronic format — such as UBL, CII, XRechnung, or Factur-X — that can be automatically processed by software without manual data entry.
FatturaPA
FatturaPA is the mandatory XML-based electronic invoice format used in Italy. Every invoice — B2B, B2C, and B2G — must be transmitted through the Sistema di Interscambio (SDI), a centralized government platform operated by the Agenzia delle Entrate (Italian Revenue Agency). The SDI validates each invoice against format and schema rules before forwarding it to the recipient. Italy was the first EU member state to mandate e-invoicing for all domestic B2B transactions, enforcing the requirement from January 1, 2019. The system follows a clearance model: invoices must be approved by the SDI before they are legally considered issued. This gives the tax authority real-time visibility into every commercial transaction. The format uses a proprietary XML schema (currently version 1.2, with technical specifications at version 1.9 as of April 2025) distinct from UBL or CII. Two transmission codes identify the invoice type: FPA12 for invoices to public administrations and FPR12 for invoices to private parties.
KSeF
KSeF (Krajowy System e-Faktur — National e-Invoice System) is Poland’s centralized government platform for issuing, receiving, and storing structured electronic invoices. Operated by the Polish Ministry of Finance, KSeF follows a clearance model: invoices must be submitted to the platform, validated, and assigned a unique KSeF ID before they are legally considered issued. Poland’s President signed the KSeF mandate into law on August 27, 2025, establishing a phased rollout beginning February 1, 2026. Large taxpayers (annual turnover exceeding PLN 200 million) were required to issue e-invoices through KSeF from that date. All other VAT-registered businesses follow from April 1, 2026, with micro-entrepreneurs joining from January 1, 2027. KSeF uses a proprietary XML schema called FA(3) — the successor to the earlier FA(2) format. Every invoice submitted to KSeF must conform to this schema. The platform validates the structure, assigns a KSeF reference number, and makes the invoice available for the buyer to retrieve. KSeF stores all invoices centrally for 10 years.
E-Invoice Formats
XRechnung
XRechnung is Germany's national implementation (CIUS) of the EN 16931 European e-invoicing standard, mandatory for all public sector invoicing in Germany.
ZUGFeRD
ZUGFeRD (Zentraler User Guide des Forums elektronische Rechnung Deutschland) is a hybrid e-invoice format that embeds machine-readable XML data inside a PDF/A-3 document. Open the file in a PDF reader — you see a normal invoice. Parse the embedded XML — you get structured data that an ERP can process automatically. ZUGFeRD 2.x and Factur-X are the same specification. They unified in 2020. The only difference is the name: ZUGFeRD is the German branding, Factur-X is the French. The underlying XML is CII (Cross Industry Invoice) D16B syntax, and the embedded file is always named factur-x.xml. The current version is ZUGFeRD 2.3.2 (aligned with Factur-X 1.07.2), released in late 2024. It’s EN 16931-compliant and accepted as a valid e-invoice format under Germany’s B2B mandate.
Factur-X
Factur-X is the Franco-German hybrid e-invoice format (identical to ZUGFeRD 2.0+) that embeds structured XML data inside a PDF/A-3 document, compliant with EN 16931.
UBL
Universal Business Language (UBL) 2.1 is an OASIS XML standard for business documents including invoices, widely used as the syntax for Peppol BIS and national e-invoicing implementations.
CII
Cross Industry Invoice (CII) is a UN/CEFACT XML syntax for electronic invoices, used as the base format for ZUGFeRD, Factur-X, and one of the two EN 16931-compliant syntaxes.
Tools & Features
Quick Start: Fix E-Invoice Errors
Invoice Navigator's Fixer tool automatically corrects technical errors in your e-invoices, making them compliant in seconds.
E-Invoice Remediation
E-invoice remediation is the controlled, automated correction of structural compliance errors in electronic invoices, with explicit safety boundaries that prevent modification of financial fields like amounts, VAT rates, and bank details.
KoSIT
KoSIT (Koordinierungsstelle für IT-Standards) is the German federal coordination office for IT standards that maintains the official validation engine for XRechnung and EN 16931 e-invoices.
an Evidence Pack
An Evidence Pack is Invoice Navigator's audit-ready compliance certificate containing the original invoice, validation results, remediation log, SHA-256 hash, QR verification code, and links to the exact rule versions used.
How to Validate E-Invoices
E-invoice validation is the process of checking a structured electronic invoice against schema, business rule, and country-specific rule sets to ensure it is compliant before submission to the buyer or tax authority.
Format Comparisons
XRechnung vs ZUGFeRD
XRechnung is a pure XML format required for German government invoicing, while ZUGFeRD is a hybrid format combining PDF and XML that works for both business and government transactions. Both comply with the European standard EN 16931, but they serve different purposes.
Peppol vs Factur-X
Peppol is a document exchange network, while Factur-X is a file format. They solve different problems and can work together—you can convert a Factur-X invoice to Peppol BIS format and send it via the Peppol network.
UBL vs CII
UBL (Universal Business Language) and CII (Cross-Industry Invoice) are two XML syntaxes for expressing EN 16931 invoices. Both carry the same business information—the difference is technical structure. Your choice usually depends on which formats and networks you need to support.
Invoice Navigator vs ecosio
Invoice Navigator and ecosio both address EU e-invoice compliance, but from different angles. Invoice Navigator is a compliance API that validates, remediates, and generates audit evidence. ecosio is a document exchange platform focused on format conversion and Peppol access point services.
Invoice Navigator vs Storecove
Invoice Navigator and Storecove both offer APIs for e-invoice compliance, but serve different parts of the pipeline. Invoice Navigator validates, remediates, and generates audit evidence. Storecove provides Peppol network connectivity with pre-flight compliance checks.
Structured E-Invoice vs PDF Invoice
EU e-invoicing mandates require structured, machine-readable invoice data. A PDF — even one sent by email — does not meet this requirement. Here’s why the distinction matters and what it means for your invoice pipeline.
Peppol vs XRechnung
Peppol and XRechnung are not competing standards — they’re complementary. Peppol is the network that delivers invoices. XRechnung is the format specification for German e-invoices. XRechnung invoices are sent via Peppol. Understanding this distinction is critical for German e-invoicing compliance.
Factur-X vs XRechnung
Factur-X embeds structured CII XML inside a PDF/A-3 container. XRechnung is pure XML — no PDF wrapper. Both are EN 16931 compliant and accepted under Germany’s B2B mandate. The choice depends on whether your recipients need a visual PDF or pure machine-to-machine data.
EN 16931 vs Peppol BIS 3.0
EN 16931 is the European content standard — it defines what data an e-invoice must contain. Peppol BIS 3.0 is a CIUS that adds rules for how invoices are structured and delivered on the Peppol network. They’re layers, not alternatives: every Peppol invoice is EN 16931 compliant, but not every EN 16931 invoice is Peppol-ready.
Peppol vs SDI (FatturaPA)
Italy’s Sistema di Interscambio (SDI) is a centralized government hub that processes every domestic e-invoice. Peppol is a federated network where certified Access Points route invoices directly between businesses. They represent fundamentally different approaches to e-invoicing infrastructure — and for businesses trading with Italy, understanding both is essential.
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