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Fatal

UBL-SR-18: An invoice can have only one buyer VAT number

In short

Fatal: fails the selected checks.

UBL-SR-18 means the invoice gives the buyer more than one VAT number (BT-48). Keep the one VAT number that applies to this sale and remove the other.

On this page

What it means

The buyer VAT number (BT-48) is the number under which the buyer is registered for VAT. In UBL it is cbc:CompanyID in a cac:PartyTaxScheme of the buyer whose cac:TaxScheme/cbc:ID is VAT, in upper or lower case. The rule allows only one such number.

Why it matters

EN 16931 allows at most one buyer VAT number per invoice or credit note.

How to fix it

Open the customer record in your invoicing software and keep one VAT number in the VAT number field. Check for a number entered twice, for example once with and once without the country prefix, or a branch number stored next to a head-office number. If the buyer has several registrations, use the one that applies to this sale. In the XML, keep one cac:PartyTaxScheme with one cbc:CompanyID and cac:TaxScheme/cbc:ID VAT under cac:AccountingCustomerParty/cac:Party.

Once the file is corrected, check it again for free: Validate an invoice against EN 16931

Or fix the invoice in a form and download the corrected file, for 1 credit: Fix a rejected e-invoice

The rule as published

Buyer VAT identifier shall occur maximum once

Where this rule applies

Rule set Version
EN 16931 (UBL) 1.3.17
EN 16931 (UBL credit note) 1.3.17
XRechnung 3.0 (UBL) 3.0.2
XRechnung 3.0 (UBL credit note) 3.0.2
Peppol BIS Billing 3.0 (invoice) 2026.5
Peppol BIS Billing 3.0 (credit note) 2026.5
SI-UBL 2.0 / NLCIUS (invoice) 2.0.3.13
SI-UBL 2.0 / NLCIUS (credit note) 2.0.3.13
France CTC (UBL invoice) 1.4.0-04
France CTC (UBL credit note) 1.4.0-04
CIUS-RO UBL Invoice 1.0.9 1.0.9
CIUS-RO UBL Credit Note 1.0.9 1.0.9
Rule text from phive-rules 4.6.4.

Check your file

Drop your e-invoice to see whether UBL-SR-18 still fails, and which other rules do.

Updated 6 November 2026