BR-O-05: Remove the VAT rate from a line that is not subject to VAT

The short answer

BR-O-05 fails when an item classified O has a cbc:Percent in its cac:Item/cac:ClassifiedTaxCategory; in the recorded example the line says 0. Delete the cbc:Percent element from that category and keep cbc:ID and cac:TaxScheme.

A rate of 0 is still a rate. A line that is not subject to VAT has no rate at all, and that absence is what tells it apart from a Zero rated line.

What the rule checks

The rule runs on each item category with cbc:ID of O under the VAT scheme, on cac:InvoiceLine and cac:CreditNoteLine alike, and reports at that cac:ClassifiedTaxCategory. Two O lines with a rate gave two findings when tried.

Whether cbc:Percent exists is all it asks. The value makes no difference: 0 fails, and so did 20 when tried.

An empty cbc:Percent is no way round it. The schema needs a number in that element, and an empty one failed the XSD layer when tried, so the EN 16931 rules never ran.

The VAT breakdown is outside this rule. When tried, a rate of 0 on the O breakdown, with none on the line, passed every layer; leaving the breakdown rate out is also allowed, because BR-48 does not require one for O.

Document-level allowances and charges have their own equivalents. An O allowance with a rate of 0 reported BR-O-06, not this rule, when tried.

How an integration ends up here

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

• The serialiser writes cbc:Percent from a rate field on every line, and untaxed items hold a rate of zero.
• One template builds the classified tax category for all categories, with the rate element always present.
• The source system cannot hold an absent rate and stores 0, which fits Zero rated lines but not O.
• The line was moved to O from Z or E in the mapping without its rate being dropped.

How to fix it

1. Check that the line is genuinely not subject to VAT. If it is really Zero rated or exempt, the category is the defect, and Z or E keep their rate of 0.
2. For O lines, omit cbc:Percent from cac:Item/cac:ClassifiedTaxCategory altogether rather than writing it empty or as 0.
3. Make the omission depend on the category in the serialiser, so the rate is written for every other category and never for O.
4. Leave the amounts alone. The line net amount and the breakdown taxable amount do not change when the rate element goes.

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: a category O item that states a rate of 0

<cac:Item>
  <cbc:Name>Example service</cbc:Name>
  <cac:ClassifiedTaxCategory>
    <cbc:ID>O</cbc:ID>
    <cbc:Percent>0</cbc:Percent>
    <cac:TaxScheme>
      <cbc:ID>VAT</cbc:ID>
    </cac:TaxScheme>
  </cac:ClassifiedTaxCategory>
</cac:Item>

Fragment of the corrected invoice: the category O item has no rate element

<cac:Item>
  <cbc:Name>Example service</cbc:Name>
  <cac:ClassifiedTaxCategory>
    <cbc:ID>O</cbc:ID>
    <cac:TaxScheme>
      <cbc:ID>VAT</cbc:ID>
    </cac:TaxScheme>
  </cac:ClassifiedTaxCategory>
</cac:Item>

The failing invoice has cbc:Percent 0 in the line cac:ClassifiedTaxCategory; the corrected invoice has no rate element there, and the O breakdown has none in either document. The failing document reports only BR-O-05, located at the classified tax category of line 1.

Where it applies

• Applies to UBL Invoice and CreditNote. In a credit note the category sits in cac:CreditNoteLine/cac:Item, and the failing invoice rewritten that way reported the same finding when tried.
• Zero rated lines work the other way round: BR-Z-05 requires a rate of 0 on them, so a mapping that moves a line between Z and O has to add or drop the element.
• An O line brings the other O rules with it: no VAT identifiers under BR-O-02, a reason on the breakdown under BR-O-10, and no other categories under BR-O-11.

Related rules

• BR-Z-05 is the opposite case, requiring a rate of 0 on Zero rated lines
• BR-48 requires a rate in every VAT breakdown except one that is not subject to VAT
• BR-O-02 applies to the same document once it has an O line, and forbids VAT identifiers
• 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 2026-09-24.1: source checked 2026-09-24, explanation last updated 2026-09-24.

The official definition of BR-O-05 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.