What it means
The rule checks cac:TaxCategory in each document-level cac:TaxTotal/cac:TaxSubtotal for cbc:PerUnitAmount. It applies to UBL invoices and credit notes. This element gives a tax amount per unit rather than a percentage. The VAT breakdown (BG-23) instead provides fields for the taxable amount (BT-116), VAT amount (BT-117) and, where applicable, VAT rate (BT-119).
Why it matters
EN 16931 does not use a per-unit tax amount in this part of the VAT breakdown.
How to fix it
Delete cbc:PerUnitAmount from cac:TaxCategory under each document-level cac:TaxTotal/cac:TaxSubtotal. If this amount represents a tax you need to account for, ask your accountant how to represent it without this element. Recheck the file.
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
A UBL invoice should not include the TaxTotal TaxSubtotal TaxCategory PerUnitAmount 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 |
Check your file
Drop your e-invoice to see whether UBL-CR-506 still fails, and which other rules do.
Related rules
- UBL-CR-507 The VAT category should not have a tier range
- UBL-CR-508 The VAT category should not have a tier rate
- UBL-CR-509 The tax scheme should not have a name
- UBL-CR-510 The tax scheme should not have a tax type code
- UBL-CR-511 The tax scheme should not have a currency code
- UBL-CR-512 The tax scheme should not have a jurisdiction address