June 21, 2026EN 169318 min readBy Eliel Nicaise

EN 16931 Mandatory Fields: Required Invoice Data

A field-by-field reference of the mandatory EN 16931 invoice fields: business term codes, formats and examples for seller, buyer, lines, VAT and totals.

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How to read this reference

EN 16931 defines a semantic data model - a list of “Business Terms” (BT) grouped into “Business Groups” (BG). This guide lists the fields you need for a compliant core invoice - every mandatory one, the main conditional ones and the key optional fields - each with its format and a realistic example.

Each field is tagged Mandatory (always required), Conditional (required when a rule applies - for example the VAT rate when the category is “standard”) or Optional (not required by core EN 16931, but listed because national rules or Peppol often make it mandatory). Beyond the core model, your country’s CIUS (a national profile such as XRechnung or the French specification) or Peppol BIS may add further mandatory fields.

The same model is expressed in two XML syntaxes - UBL 2.1 and UN/CEFACT CII (the basis of Factur-X / ZUGFeRD). The BT/BG codes below are identical in both; only the XML element names differ. The examples use a domestic sale with a 21% VAT rate.

MandatoryAlways required for a compliant invoice.

ConditionalRequired when a condition applies (see each row).

OptionalListed for reference - not required by core EN 16931, but national rules or Peppol often make it mandatory.

1. Document level

Identify the invoice itself: its number, dates, type and currency.

Code	Field	Requirement	Format	Example
BT-1	Invoice number	Mandatory	Text	INV-2026-0001
BT-2	Invoice issue date	Mandatory	YYYY-MM-DD	2026-06-21
BT-3	Invoice type code	Mandatory	UNCL 1001	380
BT-24	Specification identifier (CIUS)	Mandatory	Identifier	urn:cen.eu:en16931:2017
BT-5	Invoice currency code	Mandatory	ISO 4217	EUR
BT-10	Buyer reference	Optional	Text	PO-4567
BT-9	Payment due date	Conditional	YYYY-MM-DD	2026-07-21

2. Seller (BG-4 / BG-5)

Who issues the invoice. The country code is always mandatory; the VAT identifier is required whenever VAT is charged.

Code	Field	Requirement	Format	Example
BT-27	Seller name	Mandatory	Text	ACME GmbH
BT-31	Seller VAT identifier	Conditional	Text	DE123456789
BT-30	Seller legal registration identifier	Conditional	Text	HRB 12345
BT-34	Seller electronic address	Optional	Identifier + EAS	9930:DE123456789
BT-35	Seller address line 1	Optional	Text	Hauptstraße 1
BT-37	Seller city	Optional	Text	Berlin
BT-38	Seller post code	Optional	Text	10115
BT-40	Seller country code	Mandatory	ISO 3166-1	DE

3. Buyer (BG-7 / BG-8)

Who receives the invoice. For B2C the buyer is an individual, so the VAT identifier is left empty - but name and country code stay mandatory.

Code	Field	Requirement	Format	Example
BT-44	Buyer name	Mandatory	Text	Jane Doe
BT-48	Buyer VAT identifier	Conditional	Text	- (B2C)
BT-49	Buyer electronic address	Optional	Identifier + EAS	0002:73282932
BT-50	Buyer address line 1	Optional	Text	12 Rue de Paris
BT-52	Buyer city	Optional	Text	Lyon
BT-53	Buyer post code	Optional	Text	69001
BT-55	Buyer country code	Mandatory	ISO 3166-1	FR

4. Invoice line (BG-25)

At least one line is required. Each line describes one item with its quantity, price, net amount and VAT category.

Code	Field	Requirement	Format	Example
BT-126	Invoice line identifier	Mandatory	Text	1
BT-129	Invoiced quantity	Mandatory	Decimal	2
BT-130	Unit of measure code	Mandatory	UN/ECE Rec 20	C62
BT-153	Item name	Mandatory	Text	Wireless keyboard
BT-146	Item net price	Mandatory	Decimal	50.00
BT-131	Invoice line net amount	Mandatory	Decimal (2)	100.00
BT-151	Invoiced item VAT category code	Mandatory	UNCL 5305	S

5. VAT breakdown (BG-23)

One breakdown per VAT rate, summarising the taxable base and the tax amount. Required even for a single-rate invoice.

Code	Field	Requirement	Format	Example
BT-116	VAT category taxable amount	Mandatory	Decimal (2)	100.00
BT-117	VAT category tax amount	Mandatory	Decimal (2)	21.00
BT-118	VAT category code	Mandatory	UNCL 5305	S
BT-119	VAT category rate	Conditional	Percentage	21
BT-120	VAT exemption reason text	Conditional	Text	Exempt - Art. 44
BT-121	VAT exemption reason code	Conditional	Code	VATEX-EU-AE

6. Document totals (BG-22)

The monetary summary. These amounts must be internally consistent or the EN 16931 calculation rules will reject the invoice.

Code	Field	Requirement	Format	Example
BT-106	Sum of invoice line net amounts	Mandatory	Decimal (2)	100.00
BT-109	Invoice total amount without VAT	Mandatory	Decimal (2)	100.00
BT-110	Invoice total VAT amount	Conditional	Decimal (2)	21.00
BT-112	Invoice total amount with VAT	Mandatory	Decimal (2)	121.00
BT-115	Amount due for payment	Mandatory	Decimal (2)	121.00

Formats and code lists

EN 16931 does not let you invent values for typed fields - they must follow these standard formats and code lists.

Dates

ISO 8601 calendar date, format YYYY-MM-DD (e.g. 2026-06-21). No time or time zone on invoice dates.

Monetary amounts

Decimal with at most 2 fraction digits, a dot as decimal separator and no thousands separator (e.g. 1234.50).

Currency (BT-5)

ISO 4217 three-letter code (e.g. EUR, SEK, PLN). One document currency per invoice.

Country codes

ISO 3166-1 alpha-2 two-letter code (e.g. DE, FR, BE) for every address.

VAT category (BT-118 / BT-151)

UNCL 5305 code: S (standard), Z (zero-rated), E (exempt), AE (reverse charge), K (intra-EU), G (export), O (out of scope).

Unit of measure (BT-130)

UN/ECE Recommendation 20/21 code (e.g. C62 = one/piece, KGM = kilogram, HUR = hour, MTR = metre).

Invoice type (BT-3)

UNCL 1001 code: 380 (commercial invoice), 381 (credit note), 384 (corrected invoice), 389 (self-billed invoice).

Identifiers and schemes

Many IDs carry a scheme identifier - e.g. a seller VAT ID like DE123456789, or an electronic address qualified by a Peppol EAS scheme (such as 9930).

What changes for B2C (invoicing individuals)

EN 16931 was designed mainly for B2B and B2G, but its core model applies to any invoice - including sales to private individuals. The structure does not change; a few fields simply behave differently.

The buyer VAT identifier (BT-48) is not required for individuals - leave it out. The buyer name (BT-44) and buyer country code (BT-55) remain mandatory, and a full postal address is strongly recommended (and often required by national VAT rules).

VAT still applies in full: every line needs a VAT category code (BT-151) and the VAT breakdown (BG-23) must be present. For a normal domestic B2C sale this is category S with your national standard rate.

Routing is the real difference. The Peppol network targets B2B/B2G, so for pure B2C you still produce an EN 16931-compliant XML (for archiving, VAT/OSS reporting, or to hand to the customer) but you usually do not send it over Peppol. Always check your country's mandate - some only require structured invoices for B2B or above a threshold.

A complete example (all mandatory fields)

Here is a minimal but fully EN 16931-compliant invoice in UBL 2.1, matching the B2C example above (a €100 sale at 21% VAT). Every mandatory business term is present and labelled with its BT code.

<?xml version="1.0" encoding="UTF-8"?>
<Invoice xmlns="urn:oasis:names:specification:ubl:schema:xsd:Invoice-2"
         xmlns:cac="urn:oasis:names:specification:ubl:schema:xsd:CommonAggregateComponents-2"
         xmlns:cbc="urn:oasis:names:specification:ubl:schema:xsd:CommonBasicComponents-2">
  <cbc:CustomizationID>urn:cen.eu:en16931:2017</cbc:CustomizationID>   <!-- BT-24 -->
  <cbc:ID>INV-2026-0001</cbc:ID>                                       <!-- BT-1 -->
  <cbc:IssueDate>2026-06-21</cbc:IssueDate>                            <!-- BT-2 -->
  <cbc:DueDate>2026-07-21</cbc:DueDate>                                <!-- BT-9 -->
  <cbc:InvoiceTypeCode>380</cbc:InvoiceTypeCode>                       <!-- BT-3 -->
  <cbc:DocumentCurrencyCode>EUR</cbc:DocumentCurrencyCode>             <!-- BT-5 -->

  <cac:AccountingSupplierParty>                                        <!-- BG-4 Seller -->
    <cac:Party>
      <cac:PostalAddress>
        <cbc:StreetName>Hauptstraße 1</cbc:StreetName>                <!-- BT-35 -->
        <cbc:CityName>Berlin</cbc:CityName>                           <!-- BT-37 -->
        <cbc:PostalZone>10115</cbc:PostalZone>                        <!-- BT-38 -->
        <cac:Country><cbc:IdentificationCode>DE</cbc:IdentificationCode></cac:Country> <!-- BT-40 -->
      </cac:PostalAddress>
      <cac:PartyTaxScheme>
        <cbc:CompanyID>DE123456789</cbc:CompanyID>                    <!-- BT-31 -->
        <cac:TaxScheme><cbc:ID>VAT</cbc:ID></cac:TaxScheme>
      </cac:PartyTaxScheme>
      <cac:PartyLegalEntity>
        <cbc:RegistrationName>ACME GmbH</cbc:RegistrationName>        <!-- BT-27 -->
      </cac:PartyLegalEntity>
    </cac:Party>
  </cac:AccountingSupplierParty>

  <cac:AccountingCustomerParty>                                       <!-- BG-7 Buyer (B2C) -->
    <cac:Party>
      <cac:PostalAddress>
        <cac:Country><cbc:IdentificationCode>FR</cbc:IdentificationCode></cac:Country> <!-- BT-55 -->
      </cac:PostalAddress>
      <cac:PartyLegalEntity>
        <cbc:RegistrationName>Jane Doe</cbc:RegistrationName>         <!-- BT-44 -->
      </cac:PartyLegalEntity>
    </cac:Party>
  </cac:AccountingCustomerParty>

  <cac:TaxTotal>
    <cbc:TaxAmount currencyID="EUR">21.00</cbc:TaxAmount>             <!-- BT-110 -->
    <cac:TaxSubtotal>                                                 <!-- BG-23 VAT breakdown -->
      <cbc:TaxableAmount currencyID="EUR">100.00</cbc:TaxableAmount>  <!-- BT-116 -->
      <cbc:TaxAmount currencyID="EUR">21.00</cbc:TaxAmount>           <!-- BT-117 -->
      <cac:TaxCategory>
        <cbc:ID>S</cbc:ID>                                           <!-- BT-118 -->
        <cbc:Percent>21</cbc:Percent>                                <!-- BT-119 -->
        <cac:TaxScheme><cbc:ID>VAT</cbc:ID></cac:TaxScheme>
      </cac:TaxCategory>
    </cac:TaxSubtotal>
  </cac:TaxTotal>

  <cac:LegalMonetaryTotal>                                            <!-- BG-22 Totals -->
    <cbc:LineExtensionAmount currencyID="EUR">100.00</cbc:LineExtensionAmount> <!-- BT-106 -->
    <cbc:TaxExclusiveAmount currencyID="EUR">100.00</cbc:TaxExclusiveAmount>   <!-- BT-109 -->
    <cbc:TaxInclusiveAmount currencyID="EUR">121.00</cbc:TaxInclusiveAmount>   <!-- BT-112 -->
    <cbc:PayableAmount currencyID="EUR">121.00</cbc:PayableAmount>             <!-- BT-115 -->
  </cac:LegalMonetaryTotal>

  <cac:InvoiceLine>                                                   <!-- BG-25 Invoice line -->
    <cbc:ID>1</cbc:ID>                                               <!-- BT-126 -->
    <cbc:InvoicedQuantity unitCode="C62">2</cbc:InvoicedQuantity>     <!-- BT-129 / BT-130 -->
    <cbc:LineExtensionAmount currencyID="EUR">100.00</cbc:LineExtensionAmount> <!-- BT-131 -->
    <cac:Item>
      <cbc:Name>Wireless keyboard</cbc:Name>                         <!-- BT-153 -->
      <cac:ClassifiedTaxCategory>
        <cbc:ID>S</cbc:ID>                                           <!-- BT-151 -->
        <cbc:Percent>21</cbc:Percent>
        <cac:TaxScheme><cbc:ID>VAT</cbc:ID></cac:TaxScheme>
      </cac:ClassifiedTaxCategory>
    </cac:Item>
    <cac:Price>
      <cbc:PriceAmount currencyID="EUR">50.00</cbc:PriceAmount>       <!-- BT-146 -->
    </cac:Price>
  </cac:InvoiceLine>
</Invoice>

This is the EN 16931 core. To send it over Peppol, also add the electronic addresses (BT-34 / BT-49), the ProfileID (BT-23) and a buyer reference (BT-10). The same invoice in CII (Factur-X) uses the same BT codes with different element names.

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Frequently Asked Questions

How many fields does EN 16931 require?

The core model has around 160 business terms, but only a subset is mandatory. A minimal compliant invoice needs roughly 25–30 mandatory fields spread across the document header, the seller, the buyer, at least one line, the VAT breakdown and the totals.

Is the buyer's VAT number mandatory?

No. BT-48 is conditional - required for B2B reverse-charge or intra-EU supplies, but not for B2C sales to individuals. The buyer name and country code are always mandatory.

What date format does EN 16931 use?

ISO 8601 calendar dates, YYYY-MM-DD (e.g. 2026-06-21). Invoice dates carry no time or time-zone component.

How many decimals are allowed on amounts?

Monetary amounts use a maximum of 2 fraction digits with a dot as decimal separator. Quantities and unit prices may use more decimal places.

What is the difference between mandatory and conditional fields?

Mandatory fields must always be present. Conditional fields become mandatory when a rule applies - for example the VAT rate (BT-119) is required when the VAT category is "Standard".

Which invoice type code should I use?

BT-3 uses code list UNCL 1001. Use 380 for a commercial invoice and 381 for a credit note; 384 is a corrected invoice.

Do I need both UBL and CII?

No - choose one syntax. UBL 2.1 is common on Peppol; CII underpins Factur-X/ZUGFeRD. The mandatory business terms are identical in both.

Are there extra mandatory fields beyond the core?

Yes. National CIUS (e.g. XRechnung in Germany, the French profile) and Peppol BIS add rules - for instance XRechnung requires a buyer reference (BT-10) and seller contact details.

What VAT category code do I use for a normal domestic sale?

Category S (standard rate) with the applicable percentage in BT-119. Use Z for zero-rated, E for exempt, and AE for reverse charge.

How do I check my invoice is complete?

Validate it against the EN 16931 business rules (Schematron), not just the XSD schema. Our free UBL/Peppol validator checks mandatory fields, code lists and the EN 16931 calculation rules.