What it means
Every date checked by this rule must be exactly ten characters long, in the form YYYY-MM-DD. That covers the invoice date (BT-2), the due date (BT-9), the VAT point date (BT-7), the start and end of an invoice period (BT-73, BT-74, BT-134 and BT-135) and the delivery date (BT-72). The check also tests that the date exists, so an impossible calendar date fails. Formats with slashes or dots, a day-month-year order, a missing leading zero, or a time or time zone after the date also fail.
Why it matters
Software reads dates by their format.
How to fix it
Check how the date is stored in your invoicing software. The file must hold YYYY-MM-DD, with no time or time zone. Correct it and export again. If you build the XML yourself, write each date as plain text in cbc:IssueDate, cbc:DueDate, cbc:TaxPointDate, cbc:StartDate, cbc:EndDate and cbc:ActualDeliveryDate.
Once the file is corrected, check it again for free: Validate a Peppol BIS invoice
Or fix the invoice in a form and download the corrected file, for 1 credit: Fix a rejected e-invoice
The rule as published
Read the rule on the publisher's site
Where this rule applies
| Rule set | Version |
|---|---|
| Peppol BIS Billing 3.0 (invoice) | 2026.5 |
| Peppol BIS Billing 3.0 (credit note) | 2026.5 |
Check your file
Drop your e-invoice to see whether PEPPOL-EN16931-F001 still fails, and which other rules do.