Concept Definition
What is immutability in e-invoicing?
Immutability means that a stored invoice record cannot be modified, deleted, or overwritten after it has been issued. It is a core requirement for compliant invoice archiving. Immutability is achieved through write-once storage, cryptographic hashing, digital signatures, or blockchain timestamping.
How is immutability achieved?
Common technical methods for achieving invoice immutability include:
- Cryptographic hashing: A hash of the invoice is stored. Any change to the invoice produces a different hash, detecting tampering.
- Digital signature: The invoice is signed with a private key. The signature verifies both the issuer and that the content has not changed.
- Write-once storage: Invoices are stored in append-only systems that prohibit modification (e.g., WORM storage).
- Blockchain timestamping: Invoice hash recorded on a blockchain provides an immutable timestamp proof.
Frequently Asked Questions
- If an invoice has an error, how is it corrected without breaking immutability?
- Errors in issued invoices are corrected by issuing a credit note (to fully or partially cancel the original) and optionally a corrective invoice. The original invoice remains in the archive unchanged. The correction creates a new, separate document that references the original.
- Is immutability required by law?
- Yes. EU VAT rules require that the authenticity and integrity of invoice content be guaranteed throughout the retention period. Immutability is the technical implementation of this legal requirement. French DGFiP rules explicitly require that archived invoices cannot be modified.