BR-O-06: Remove the VAT rate from a document level allowance that is not subject to VAT

The short answer

BR-O-06 fails when a cac:AllowanceCharge with cbc:ChargeIndicator false has a cac:TaxCategory of O that contains cbc:Percent. The recorded example gives the Loyalty discount of 5.00 a rate of 0. Delete that element and keep cbc:ID and cac:TaxScheme as they are.

For a Zero rated or exempt allowance the rate element is how it says 0. For O the absence of the element is the statement, just as the O breakdown in the recorded example carries none.

What the rule checks

Every allowance whose tax category is O under the VAT scheme is tested, and the finding points at that cac:TaxCategory. Nothing ties the rule to the document root, so a line-level allowance counts too: when tried, one in O with a rate of 0 reported this rule at the line, with the warning UBL-CR-558 for a tax category on a line allowance.

Only the presence of the element matters. The recorded 0 fails, and when tried a rate of 20 on the same loyalty discount gave the same single finding.

Writing the element empty is no way out: an empty cbc:Percent in the discount's tax category failed the XSD layer when tried, so no business rule ran.

This rule reads allowances only. An O charge with a rate is reported by BR-O-07, and an O line with one by BR-O-05.

How an integration ends up here

Possible causes, from the shape of the rule rather than from measured usage:

• The allowance serialiser writes a rate for every category and stores zero for categories without VAT.
• The discount was first set up as Zero rated with a rate of 0, and later moved to O by changing only its code.
• The source system cannot hold an empty rate on an allowance and sends 0 in its place.

How to fix it

1. Make sure the allowance really belongs in O: it should reduce amounts that are themselves not subject to VAT, as the line of 25.00 is in the recorded example.
2. Delete cbc:Percent from the allowance's cac:TaxCategory, leaving cbc:ID O followed directly by cac:TaxScheme.
3. Leave the amounts as they are. The allowance still takes the O taxable amount from 25.00 to 20.00, with or without the rate element.
4. In the serialiser, write the allowance rate for every category except O.

Validate your corrected invoice

Before and after

These are fragments, not complete documents. The complete synthetic documents they come from are linked below.

Fragment of the failing invoice: the O loyalty discount states a rate of 0

<cac:AllowanceCharge>
  <cbc:ChargeIndicator>false</cbc:ChargeIndicator>
  <cbc:AllowanceChargeReasonCode>95</cbc:AllowanceChargeReasonCode>
  <cbc:AllowanceChargeReason>Loyalty discount</cbc:AllowanceChargeReason>
  <cbc:Amount currencyID="GBP">5.00</cbc:Amount>
  <cac:TaxCategory>
    <cbc:ID>O</cbc:ID>
    <cbc:Percent>0</cbc:Percent>
    <cac:TaxScheme>
      <cbc:ID>VAT</cbc:ID>
    </cac:TaxScheme>
  </cac:TaxCategory>
</cac:AllowanceCharge>

Fragment of the corrected invoice: the O loyalty discount has no rate element

<cac:AllowanceCharge>
  <cbc:ChargeIndicator>false</cbc:ChargeIndicator>
  <cbc:AllowanceChargeReasonCode>95</cbc:AllowanceChargeReasonCode>
  <cbc:AllowanceChargeReason>Loyalty discount</cbc:AllowanceChargeReason>
  <cbc:Amount currencyID="GBP">5.00</cbc:Amount>
  <cac:TaxCategory>
    <cbc:ID>O</cbc:ID>
    <cac:TaxScheme>
      <cbc:ID>VAT</cbc:ID>
    </cac:TaxScheme>
  </cac:TaxCategory>
</cac:AllowanceCharge>

The failing invoice has cbc:Percent 0 between cbc:ID and cac:TaxScheme in the tax category of the Loyalty discount; in the corrected invoice that element is absent. Nothing else differs, and the failing document reports only BR-O-06, located at the cac:TaxCategory of the first cac:AllowanceCharge.

Where it applies

• Applies to UBL Invoice and CreditNote, where the allowance has the same shape. Rewritten as a credit note, the failing invoice reported this rule alone when tried.
• Allowances in other nil-VAT categories work the other way: a Zero rated or exempt allowance needs a rate of 0 (BR-Z-06, BR-E-06), so moving an allowance between those categories and O means adding or removing the element.
• The same allowance, while in O, also rules out VAT identifiers under BR-O-03 and is deducted in the O taxable amount checked by BR-O-08.

Related rules

• BR-O-05 forbids the same rate element on a line that is not subject to VAT
• BR-O-07 forbids it on a document level charge in category O
• BR-Z-06 requires the rate of 0 on a Zero rated allowance that this rule forbids for O
• BR-O-03 forbids VAT identifiers on a document with a not subject to VAT allowance
• Browse every rule in the reference
• Background: Understanding EN 16931 validation errors

Scope and source

Written for Peppol BIS Billing 3.0.21 (May 2026), EN 16931 1.3.16, as applied to UBL 2.1 Invoice and CreditNote documents. Other profiles, syntaxes and releases can define this identifier differently. Guidance version 2026-09-28.1: source checked 2026-09-28, explanation last updated 2026-09-28.

The official definition of BR-O-06 carries the normative wording and test. This page is our explanation of it, not a copy.

Guidance does not change the engine verdict. Fixing this finding does not mean the document passes every layer, and validation does not certify legal or tax compliance or transmit a document over Peppol.