What it means
The rule looks at the discounts (BG-20) and charges (BG-21) placed on the whole invoice, directly under the invoice or credit note. It warns when the cac:TaxCategory inside one of them has a cbc:BaseUnitMeasure, the unit that a tax per unit is based on. EN 16931 has no such element for a discount or charge.
Why it matters
EN 16931 does not use cbc:BaseUnitMeasure in the VAT category of document-level discounts (BG-20) or charges (BG-21).
How to fix it
Delete cbc:BaseUnitMeasure from the cac:TaxCategory inside each cac:AllowanceCharge directly under the Invoice or CreditNote element. Check that any VAT rate on the discount or charge is a percentage and matches the VAT breakdown. Export the corrected file and check it again.
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 AllowanceCharge TaxCategory BaseUnitMeasure 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-478 still fails, and which other rules do.
Related rules
- UBL-CR-479 Do not give a VAT amount per unit on an invoice-level discount or charge
- UBL-CR-480 Do not put an exemption reason code on an invoice-level discount or charge
- UBL-CR-481 Do not put an exemption reason text on an invoice-level discount or charge
- UBL-CR-482 Do not give a tier range on the VAT of a discount or charge
- UBL-CR-483 Leave TierRatePercent out of discount and charge VAT categories
- UBL-CR-484 Leave the tax scheme name out of discounts and charges