Guidance published ahead of the 1 September 2026 go-live stresses two practical points. First, validate invoice numbers upstream, in your own system, before sending: once invoices flow through approved platforms, a repeated invoice number is a common cause of outright rejection. This especially catches businesses where two people, or two systems such as a till and an accounting package, both issue invoices and the numbering overlaps. Second, the invoice must remain legally correct in its own right even when your platform routes it using a technical identifier — a routing code is not a substitute for the details the law requires on the invoice itself.
What to do
1
Turn on duplicate invoice-number checking in your invoicing or accounting software.
2
Make sure invoice numbering is a single unbroken sequence, especially if more than one person or system issues invoices.
3
Send a few test invoices through your platform and confirm they are accepted before you rely on the flow.
4
Keep every legally required invoice detail complete even when your platform adds its own routing identifiers.
Sources: VATupdate — French e-invoicing requires upstream validation to prevent invoice number duplication (28 Aug 2026) · VATupdate — French e-invoices must remain legally correct even where technical routing uses other identifiers (25 Aug 2026)
✓ Verified against sources on 2026-09-01 · updated when the regulation changes