Electronic invoices with signatures: tax compliance 2026

The dematerialisation of invoices is no longer optional: since the progressive entry into force of the electronic invoicing requirement in France, driven by Ordinance No. 2021-1190 of 15 September 2021 and subsequent implementation decrees, businesses subject to VAT must issue, transmit and receive their invoices in approved digital formats. Among the central issues is the digital signature of electronic invoices, guaranteeing authenticity, integrity and tax compliance. This article explores the accepted formats, legal obligations, required signature levels and best practices to adopt to secure your processes in 2026.

Why digital signature is at the heart of electronic invoicing

The Directorate General for Public Finance (DGFiP) imposes three cumulative conditions for an electronic invoice to be fiscally admissible: authenticity of origin, integrity of content and readability of the document (Article 289 of the General Tax Code). Advanced or qualified electronic signature constitutes one of three expressly recognised means to satisfy these requirements — alongside the reliable audit trail (PAF) and fiscal EDI.

The three compliance routes according to the CGI

The General Tax Code, in Articles 289 and 289 bis, clearly distinguishes:

• Advanced electronic signature based on a qualified certificate (in accordance with the eIDAS regulation), which guarantees the identification of the signatory and the integrity of the document from its creation;
• Fiscal EDI (Electronic Data Interchange), governed by strict protocols of mutual authentication;
• Reliable audit trail, which imposes complete process documentation, often costly to maintain for SMEs.

For the vast majority of businesses, digital signature on approved XML formats remains the most legally robust solution and the most technically scalable. It integrates natively into dematerialised flows and can be automatically verified by dematerialisation partner platforms (PDP) and the Public Invoicing Portal (PPF).

What digital signature concretely guarantees on an invoice

A qualified electronic signature affixed to an invoice guarantees four essential properties:

1. Authenticity: the qualified certificate definitively identifies the invoice issuer;
2. Integrity: any modification post-signature is cryptographically detectable;
3. Non-repudiation: the issuer cannot deny having produced the invoice;
4. Time-stamping: the date and time of issue are certified, which may prove decisive in the event of tax or commercial dispute.

To deepen the technical and legal foundations, consult our complete guide to electronic signature, which details the different signature levels and their use cases.

XML formats and digital signatures: which to choose in 2026?

The electronic invoicing ecosystem is based on structured formats whose digital signature must be technically compatible. In 2026, three formats dominate the French and European market.

Factur-X: the Franco-German hybrid format of reference

Factur-X (called ZUGFeRD in Germany) is a hybrid PDF/A-3 format integrating a structured XML file (compliant with the EN 16931 standard). It is popular for its dual readability: a PDF readable by humans, an XML processable automatically by ERPs and accounting solutions.

The signature of a Factur-X document is performed by signing the PDF/A-3 container, which simultaneously covers the visual part and the embedded XML flow. The standard ETSI EN 319 132 (XAdES) or ETSI EN 319 122 (CAdES) applies according to the implementation chosen.

Key data on Factur-X:

• Minimum profile: basic identification data, suitable for micro-enterprises;
• EN 16931 profile (called "Comfort"): complete data compliant with Directive 2014/55/EU;
• Extended profile: additional data for sectors with high automation needs (distribution, industry).

UBL and CII: European standards to know

Universal Business Language (UBL) and Cross Industry Invoice (CII) are the two XML syntaxes recognised by the European EN 16931 standard. The PPF and approved PDPs have accepted these two formats since 2025.

The signature of an invoice in pure UBL or CII XML follows the XAdES (XML Advanced Electronic Signatures) specification, standardised by ETSI. The variant XAdES-B-LT (Long-Term) is recommended to guarantee the verifiability of the signature over the legal retention period for invoices (10 years under French tax law).

How to choose the right signature level for your invoices?

The eIDAS regulation and its signature levels define three levels: simple, advanced and qualified. For electronic invoices:

• Advanced signature based on a qualified certificate: minimum level recommended by the DGFiP;
• Qualified signature (QES): highest level, not open to challenge in the event of tax or commercial dispute, recommended for high-stakes invoices (public procurement, major customers, intra-community transactions).

Simple signature is not sufficient to meet the requirements of Article 289 CGI.

Tax obligations: what the DGFiP actually monitors

The DGFiP has had access to invoicing data via the PPF since 2024. Inspections focus on several dimensions that digital signature directly secures.

The mandatory data of a compliant electronic invoice

In application of Article 242 nonies A of Annex II to the CGI, an electronic invoice must include as a minimum:

• The SIREN number of the issuer and recipient;
• The nature of operations (delivery of goods, provision of services, mixed operation);
• Payment status;
• The date of delivery or performance of the service.

This data now flows to the administration via the PPF or PDPs. Electronic signature certifies that this data has not been altered between issue and receipt by the administration.

Retention and archival of signed invoices

The retention of signed electronic invoices is subject to strict rules:

• 6 years minimum retention for tax audit purposes (Book of Fiscal Procedures, Article L102 B);
• 10 years in the practice recommended by accountants, consistent with commercial prescription;
• The integrity of the signature must be verifiable throughout the retention period, which requires using signature formats with guaranteed longevity (XAdES-B-LT or XAdES-B-LTA with qualified time-stamping).

The qualified electronic time-stamping plays a critical role here: it freezes the date of signature creation and allows proof that the certificates used were valid at the time of signing, even if those certificates have since expired.

Risks in case of non-compliance

An electronic invoice that is non-compliant (absence of valid signature, non-approved format, missing data) exposes the business to:

• Rejection of VAT deductibility on corresponding purchases (Article 272 CGI);
• Tax penalties that can reach €15 per non-compliant invoice, with a minimum of €60 per transaction (Article 1737 CGI);
• A risk of adjustment during a tax audit, if the administration contests the authenticity or integrity of the invoices presented.

Technical integration: connecting signature to your invoicing flows

The major operational challenge of 2026 is the seamless integration of electronic signature into existing processes, without friction for accounting and finance teams.

Signature APIs and connection to ERPs

Modern electronic signature solutions expose REST APIs allowing the automation of invoice signature on the fly, directly from ERPs (SAP, Oracle, Sage, Cegid, etc.) or invoicing platforms (Chorus Pro for public procurement, private PDPs for the private sector).

A typical flow for issuing a signed electronic invoice includes:

1. Generation of the XML or Factur-X file by the ERP;
2. API call to the signature solution (e.g. Certyneo) to affix the XAdES-B-LT signature with the company's qualified certificate;
3. Transmission of the signed invoice to the PPF or PDP;
4. Automatic archival in the digital safe.

Qualified certificates: who issues them and how to obtain them?

In France, qualified electronic signature certificates are issued by Qualified Trust Service Providers (PSCQ) listed in the national trust list (TSL), published and maintained by ANSSI. Among active PSCQs in 2026: Certigna, ChamberSign, Certinomis, or even European players like Qualified Trust Service Providers referenced in the European Trust List.

Certificates are issued after identity verification of the company's legal representative or authorised signatory, either face-to-face or by video identification depending on the provider. The standard validity period is 1 to 3 years.

To compare available solutions on the market and choose the one suited to your invoicing volume, our comparison of electronic signature solutions provides you with an objective analysis grid based on eIDAS criteria, cost per signature and API integration capabilities.

Sealing versus signature: a distinction not to be overlooked

In the context of automated invoicing, an important technical distinction must be made: electronic signature (commitment by an identified natural person) and electronic seal (commitment by a legal entity, without identification of a specific individual). The eIDAS regulation explicitly provides for qualified electronic seals (Article 35 eIDAS) for legal entities.

For electronic invoicing in automated flow, qualified electronic seal is often more appropriate: it identifies the issuing company without requiring the intervention of an individual signatory for each invoice. The DGFiP recognises both modalities as long as the underlying certificate is qualified within the meaning of eIDAS.

The legal value of electronic signature in the commercial and tax context is detailed in our dedicated guide, which also addresses the nuances between signature and seal for legal entities.

Applicable legal framework for signed electronic invoices

The compliance of signed electronic invoices is based on a layering of regulatory texts that is essential to master.

Civil Code, Articles 1366 and 1367: Article 1366 establishes the principle of equivalence between electronic writing and paper writing, subject to the person's identity being duly assured and the document being prepared and retained under conditions that guarantee its integrity. Article 1367 defines electronic signature as the use of a reliable identification process guaranteeing its connection to the deed to which it attaches.

eIDAS Regulation No. 910/2014 of the European Parliament and Council: this regulation establishes the common legal framework for trust services in the European Union. It defines three signature levels (simple, advanced, qualified), the requirements applicable to qualified trust service providers and the legal effects of each signature level. Qualified electronic signature has the legal effect of a handwritten signature in all Member States (Article 25.2 eIDAS). eIDAS 2.0 (Regulation 2024/1183), which entered into progressive application from 2025, strengthens interoperability requirements and introduces the European digital identity wallet (EUDIW).

General Tax Code, Articles 289 and 289 bis: Article 289 CGI sets out the three compliance routes for electronic invoices (advanced electronic signature with qualified certificate, fiscal EDI, reliable audit trail). Article 289 bis clarifies the arrangements applicable to EDI. Article 242 nonies A of Annex II lists the 25 mandatory invoicing particulars, several of which are now transmitted electronically to the DGFiP via the PPF.

Book of Fiscal Procedures, Article L102 B: requires retention of supporting documents for a period of 6 years from the date they were established or received. For invoices, professionals recommend retention of 10 years in line with commercial prescription periods (Article L110-4 of the Commercial Code).

Ordinance No. 2021-1190 of 15 September 2021 and implementation decrees: establish the progressive obligation of electronic invoicing for those subject to VAT established in France, with rollout milestones between 2026 and 2027 depending on business size.

ETSI standards EN 319 132 (XAdES) and EN 319 122 (CAdES): European technical standards defining advanced electronic signature formats on XML documents and binary data. The XAdES-B-LT profile is recommended for invoices, due to its ability to maintain signature verifiability over the long term.

GDPR No. 2016/679: personal data contained in invoices (individual customer names, contact details) are subject to the principles of minimisation, security and limitation of retention period. Electronic signature also involves the processing of signatory identity data, governed by GDPR and the certification policies of PSCQs.

Legal and tax risks: an electronic invoice whose signature is invalid, expired or produced with a non-qualified certificate may be reclassified by the administration as not meeting the requirements of Article 289 CGI, resulting in rejection of deductible VAT and penalties of up to 50% of amounts reassessed in case of proven bad faith (Article 1729 CGI).

Use scenarios: digital invoice signature in practice

Scenario 1: an industrial SME with high supplier invoicing volume

An industrial SME handling approximately 3,500 supplier invoices per year was facing two recurring problems: manual validation delays extending the payment cycle to an average of 45 days, and occasional VAT deductibility rejections during tax audits due to invoices received without valid signature or documented audit trail.

By deploying a digital signature API solution integrated directly into its ERP, the company automated the qualified sealing of each issued invoice and implemented automatic validity control of signatures on received invoices. Results observed after 12 months: reduction of payment cycle from 45 to 18 days (-60%), zero VAT rejection during the following tax audit, and estimated savings of 35% on invoice administrative processing costs (range consistent with Gartner 2025 benchmarks for accounting dematerialisation).

Scenario 2: an accounting firm managing the invoicing of 80 SME/SMB clients

An accounting firm with about fifteen employees, mandated to manage the accounting and invoice production for its client structures, had to ensure the compliance of invoices issued on behalf of each of its legal entities, with distinct certificates per entity.

The firm opted for a multi-entity signature platform allowing it to manage a portfolio of qualified certificates per client, with complete traceability of signatures and automatic archival in individual digital safes. Estimated time saving: 4 to 6 hours per month per client on manual validation and archival tasks, representing a potential of 320 to 480 hours freed annually for the firm, reallocated to added-value missions (tax advice, strategic support).

Scenario 3: a digital services company responding to public procurement

A 100-employee IT services company, operating primarily with public-sector customers via Chorus Pro, had to ensure that each of its issued invoices complied with the qualified electronic signature requirements imposed by certain public contracting authorities.

By connecting its electronic signature solution to its invoicing tool via REST API, the company now automatically generates Factur-X format invoices signed with qualified electronic seal, transmitted directly to Chorus Pro. Compliance is verifiable in real time by the contracting authority. No rejections due to technical non-compliance have been recorded since go-live, compared to 3 to 4 quarterly rejections previously related to format errors or absence of valid signature. This type of approach is fully in line with electronic signature for law firms and service companies, a sector particularly exposed to documentary compliance requirements.

Conclusion

Signed electronic invoices are no longer a subject reserved for IT departments: they are now at the heart of the tax and accounting obligations of every business subject to VAT in France. Mastering approved XML formats (Factur-X, UBL, CII), choosing the right signature level (advanced or qualified), and integrating a signature process into your invoicing flows are the three pillars of sustainable compliance in 2026 and beyond.

Qualified digital signature simultaneously guarantees the authenticity of the issuer, the integrity of the data and the tax admissibility of invoices — whilst reducing processing times and risks of adjustment.

Certyneo provides a qualified electronic signature API solution natively compatible with Factur-X, UBL and CII formats, integratable into your ERP or PDP in just a few hours. Discover our pricing and start your free trial to secure your electronic invoicing today.