E-Invoicing Conformance Levels: BASIC, EN 16931, and EXTENDED Explained

In European e-invoicing, conformance levels define different tiers of data completeness and structure according to the **EN 16931 standard** . This is an easy to follow guide.

Pigeon AI Pigeon AI
November 29, 2025 6 min read

Introduction

In European e-invoicing, conformance levels define different tiers of data completeness and structure according to the EN 16931 standard (the European norm for electronic invoicing). These levels are particularly relevant for formats like Factur-X/ZUGFeRD that embed XML data in PDFs.

Understanding these conformance levels is crucial for implementing compliant e-invoicing solutions, especially when dealing with cross-border transactions, B2G (business-to-government) invoicing, or automated accounts payable systems.

The Three Main Conformance Levels

BASIC (and BASIC WL - Without Lines)

The BASIC level represents the minimum viable invoice structure. It comes in two variants:

  • BASIC (with lines): Contains header information plus line-item details
  • BASIC WL (Without Lines): Contains only invoice header and summary information, no line-item details

This level covers essentials like seller/buyer information, totals, payment terms, and tax summaries. It has the smallest data footprint and is useful for simple invoices or scenarios where line details aren't required for processing (such as expense reports or simple statements).

EN 16931 (COMFORT in ZUGFeRD)

This is the core compliance level mandated by the EU directive. It includes:

  • All mandatory fields required by EN 16931-1
  • Both header and complete line-item information
  • All necessary references (PO, contract, delivery, etc.)
  • Standard business requirements across EU member states

This is what most B2G (business-to-government) invoicing requires and represents the sweet spot for EU compliance - it ensures legal compliance while keeping the data model manageable.

EXTENDED

The EXTENDED level is a superset of EN 16931 that includes:

  • All EN 16931 fields plus additional optional elements
  • Industry-specific or national extensions
  • Logistics data, customs information, and detailed item attributes
  • Maximum data richness but larger file sizes

You'd only use EXTENDED when you need specific additional data that EN 16931 doesn't cover, and typically requires agreement between trading partners on which extensions to use.

Detailed Comparison Table

Below is a comprehensive breakdown showing which elements are mandatory (✅), optional (🟡), or not supported (❌) in each conformance level:

Element Category BASIC (with Lines) BASIC WL EN 16931 EXTENDED
HEADER - Basic Info
Invoice number ✅ Mandatory ✅ Mandatory ✅ Mandatory ✅ Mandatory
Invoice date ✅ Mandatory ✅ Mandatory ✅ Mandatory ✅ Mandatory
Invoice currency ✅ Mandatory ✅ Mandatory ✅ Mandatory ✅ Mandatory
Invoice type code ✅ Mandatory ✅ Mandatory ✅ Mandatory ✅ Mandatory
Seller name ✅ Mandatory ✅ Mandatory ✅ Mandatory ✅ Mandatory
Seller postal address ✅ Mandatory ✅ Mandatory ✅ Mandatory ✅ Mandatory
Seller country code ✅ Mandatory ✅ Mandatory ✅ Mandatory ✅ Mandatory
Seller VAT identifier ✅ Mandatory* ✅ Mandatory* ✅ Mandatory* ✅ Mandatory*
Buyer name ✅ Mandatory ✅ Mandatory ✅ Mandatory ✅ Mandatory
Buyer postal address ✅ Mandatory ✅ Mandatory ✅ Mandatory ✅ Mandatory
Buyer country code ✅ Mandatory ✅ Mandatory ✅ Mandatory ✅ Mandatory
Payment terms description 🟡 Optional 🟡 Optional 🟡 Optional 🟡 Optional
Payment due date 🟡 Optional 🟡 Optional 🟡 Optional 🟡 Optional
Payment account identifier (IBAN) 🟡 Optional 🟡 Optional 🟡 Optional 🟡 Optional
Payment account name 🟡 Optional 🟡 Optional 🟡 Optional 🟡 Optional
HEADER - Extended Info
Buyer VAT identifier ❌ ❌ 🟡 Optional 🟡 Optional
Seller electronic address ❌ ❌ 🟡 Optional 🟡 Optional
Buyer electronic address ❌ ❌ 🟡 Optional 🟡 Optional
Seller identifier ❌ ❌ 🟡 Optional 🟡 Optional
Buyer identifier ❌ ❌ 🟡 Optional 🟡 Optional
Seller legal registration ID ❌ ❌ 🟡 Optional 🟡 Optional
Buyer legal registration ID ❌ ❌ 🟡 Optional 🟡 Optional
Seller contact point ❌ ❌ 🟡 Optional 🟡 Optional
Buyer contact point ❌ ❌ 🟡 Optional 🟡 Optional
Seller tax representative ❌ ❌ 🟡 Optional 🟡 Optional
Purchase order reference ❌ ❌ 🟡 Optional 🟡 Optional
Sales order reference ❌ ❌ 🟡 Optional 🟡 Optional
Contract reference ❌ ❌ 🟡 Optional 🟡 Optional
Project reference ❌ ❌ 🟡 Optional 🟡 Optional
Tender/lot reference ❌ ❌ 🟡 Optional 🟡 Optional
Delivery location ❌ ❌ 🟡 Optional 🟡 Optional
Delivery date/period ❌ ❌ 🟡 Optional 🟡 Optional
Invoicing period (start/end) ❌ ❌ 🟡 Optional 🟡 Optional
Preceding invoice reference ❌ ❌ 🟡 Optional 🟡 Optional
Ship-to party ❌ ❌ ❌ 🟡 Optional
Invoice recipient (if different) ❌ ❌ ❌ 🟡 Optional
Department/cost center codes ❌ ❌ ❌ 🟡 Optional
Multiple contact persons ❌ ❌ ❌ 🟡 Optional
Buyer accounting reference ❌ ❌ ❌ 🟡 Optional
TAX
Tax category code ✅ Mandatory ✅ Mandatory ✅ Mandatory ✅ Mandatory
Tax rate (percentage) ✅ Mandatory ✅ Mandatory ✅ Mandatory ✅ Mandatory
Tax category taxable amount ✅ Mandatory ✅ Mandatory ✅ Mandatory ✅ Mandatory
Tax category tax amount ✅ Mandatory ✅ Mandatory ✅ Mandatory ✅ Mandatory
Tax exemption reason code ❌ ❌ 🟡 Conditional** 🟡 Conditional**
Tax exemption reason text ❌ ❌ 🟡 Conditional** 🟡 Conditional**
Tax point date ❌ ❌ 🟡 Optional 🟡 Optional
VAT accounting currency ❌ ❌ 🟡 Optional 🟡 Optional
Local/additional tax types ❌ ❌ ❌ 🟡 Optional
Multiple tax schemes ❌ ❌ ❌ 🟡 Optional
DOCUMENT-LEVEL CHARGES
Document charges supported ❌ ❌ 🟡 Optional 🟡 Optional
Charge amount ❌ ❌ ✅ Mandatory*** ✅ Mandatory***
Charge base amount ❌ ❌ 🟡 Optional 🟡 Optional
Charge percentage ❌ ❌ 🟡 Optional 🟡 Optional
Charge reason code ❌ ❌ 🟡 Optional 🟡 Optional
Charge reason text ❌ ❌ 🟡 Optional 🟡 Optional
Charge tax category ❌ ❌ ✅ Mandatory*** ✅ Mandatory***
Charge tax rate ❌ ❌ ✅ Mandatory*** ✅ Mandatory***
Multiple charges simultaneously ❌ ❌ ❌ 🟡 Optional
Charge sequence number ❌ ❌ ❌ 🟡 Optional
DOCUMENT-LEVEL ALLOWANCES