PEPPOL-EN16931-R121: Price base quantity is zero or negative

StandardPeppol BIS Billing 3.0 (OpenPeppol)SeverityError: the invoice is rejectedSyntaxUBL, CIIApplies toInvoices and credit notes sent over the Peppol network (UBL) and, because XRechnung embeds the Peppol rule set, every XRechnung as well.

Official rule text

[PEPPOL-EN16931-R121] Base quantity MUST be a positive number above zero.

Why this error occurs

The item price base quantity (BT-149) is the divisor in the line calculation (quantity x price / base quantity), so it must be a positive number greater than zero. The rule checks cac:Price/cbc:BaseQuantity (UBL) or ram:BasisQuantity in ram:NetPriceProductTradePrice and ram:GrossPriceProductTradePrice (CII) when present. It nearly always comes from an ERP exporting a default of 0 for the price unit, or from a negative value on credit lines.

How to fix it

Set cbc:BaseQuantity / ram:BasisQuantity to the number of units the price refers to: 1 for a price per unit, 100 for a price per 100 units. If your system has no price unit concept, omit the element entirely; the standard then assumes 1. Never use 0 or a negative value, and give the attribute unitCode with the same code as the invoiced quantity.

Example (valid)

<cac:Price>
  <cbc:PriceAmount currencyID="EUR">12.50</cbc:PriceAmount>
  <cbc:BaseQuantity unitCode="C62">100</cbc:BaseQuantity>
</cac:Price>

What the validator checks

Checked element (context):

UBL

cac:InvoiceLine | cac:CreditNoteLine

Test (XPath):

not(cac:Price/cbc:BaseQuantity) or xs:decimal(cac:Price/cbc:BaseQuantity) > 0

CII

ram:NetPriceProductTradePrice | ram:GrossPriceProductTradePrice

Test (XPath):

not(ram:BasisQuantity) or xs:decimal(ram:BasisQuantity) > 0

Check your invoice

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Same check via API:

curl -F file=@invoice.xml https://einvoicechecker.com/v1/validate

Related rules

PEPPOL-EN16931-R001 Business process identifier (BT-23) is missing
PEPPOL-EN16931-R002 No more than one note is allowed on document level, unless both the buyer and seller…
PEPPOL-EN16931-R003 Neither buyer reference nor purchase order reference given
PEPPOL-EN16931-R004 Specification identifier is not the Peppol BIS Billing 3.0 identifier
PEPPOL-EN16931-R005 VAT accounting currency equals the invoice currency
PEPPOL-EN16931-R006 Only one invoiced object is allowed on document level
PEPPOL-EN16931-R007 Business process identifier has the wrong format
PEPPOL-EN16931-R008 Document contains empty elements

Frequently asked questions

What does PEPPOL-EN16931-R121 mean?

PEPPOL-EN16931-R121 is a peppol bis billing 3.0 rule: Base quantity MUST be a positive number above zero.

Will my invoice be rejected because of PEPPOL-EN16931-R121?

Yes. PEPPOL-EN16931-R121 is flagged "fatal"; validators (KoSIT, Peppol access points, the German ZRE/OZG-RE portals) reject the invoice until it is fixed.

Which formats does PEPPOL-EN16931-R121 apply to?

Invoices and credit notes sent over the Peppol network (UBL) and, because XRechnung embeds the Peppol rule set, every XRechnung as well. Syntax: UBL and CII.

Source: Peppol BIS Billing 3.0.20 (November 2025). Catalogue generated from the official schematron on 2026-10-14.