What it means
The invoice period (BG-14) says which stretch of time the invoice covers, with fields for a start date (BT-73) and an end date (BT-74), for example a subscription month. The rule counts the cac:InvoicePeriod elements directly under the invoice or credit note and allows one. Periods on individual lines (BG-26) are separate and not counted by this rule.
Why it matters
EN 16931 has a single invoice period for the whole document.
How to fix it
In your invoicing software, find the billing or service period at the top of the invoice and keep one period. If different lines cover different periods, set the period on those lines instead. In the XML, keep one cac:InvoicePeriod directly under the invoice or credit note.
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
Invoice period 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 |
Check your file
Drop your e-invoice to see whether UBL-SR-08 still fails, and which other rules do.
Related rules
- UBL-SR-09 An invoice can have only one seller name
- UBL-SR-10 An invoice can have only one seller trading name
- UBL-SR-11 An invoice can have only one seller company registration number
- UBL-SR-12 An invoice can have only one seller VAT number
- UBL-SR-13 An invoice can have only one seller tax number
- UBL-SR-14 Seller additional legal information can be given only once