Electronic invoices with signatures: tax compliance 2026

The dematerialisation of invoices is no longer optional: since the progressive implementation of the electronic invoicing obligation in France, driven by Order No. 2021-1190 of 15 September 2021 and subsequent implementing decrees, companies 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 of Public Finance (DGFiP) imposes three cumulative conditions for an electronic invoice to be fiscally acceptable: 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 reliable audit trail (PAF) and fiscal EDI.

The three routes to compliance 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 identification of the signatory and integrity of the document from its creation;
• Fiscal EDI (Electronic Data Interchange), governed by strict protocols of mutual authentication;
• Reliable audit trail, which requires complete process documentation, often costly to maintain for SMEs.

For the vast majority of companies, digital signature on approved XML formats remains the most legally robust solution and the most technically scalable. It integrates natively in dematerialised flows and can be automatically verified by dematerialisation platform partners (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 post-signature modification is cryptographically detectable;
3. Non-repudiation: the issuer cannot deny having produced the invoice;
4. Timestamping: the date and time of issue are certified, which can prove critical in case of tax or commercial dispute.

To deepen your understanding of the technical and legal foundations, consult our comprehensive 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 built 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 reference format

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 favoured for its dual readability: a PDF readable by humans, an XML processable automatically by ERPs and accounting solutions.

Signing a Factur-X document is done 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 depending on the implementation chosen.

Key data on Factur-X:

• Minimum profile: basic identification data, suitable for microenterprises;
• EN 16931 profile (called "Comfort"): complete data compliant with European Directive 2014/55/EU;
• Extended profile: additional data for sectors with high automation requirements (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 standard EN 16931. The PPF and approved PDPs have accepted both formats since 2025.

Signing an invoice in pure UBL or CII XML follows the XAdES (XML Advanced Electronic Signatures) specification, standardised by ETSI. The XAdES-B-LT (Long-Term) variant is recommended to ensure signature verifiability throughout the legal invoicing retention period (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 DGFiP;
• Qualified signature (QES): highest level, unarguable in case of tax or commercial dispute, recommended for high-stakes invoices (public procurement, major accounts, intra-Community operations).

Simple signature is not sufficient to satisfy the requirements of article 289 CGI.

Tax obligations: what DGFiP really controls

DGFiP has had access to invoicing data via the PPF since 2024. Controls cover 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 contain as a minimum:

• The SIREN number of the issuer and recipient;
• The nature of the operations (delivery of goods, provision of services, mixed operation);
• The payment status;
• The delivery date or execution date 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 archiving of signed invoices

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

• 6 years minimum retention for tax audit purposes (Tax Procedure Book, article L102 B);
• 10 years in practice recommended by accountants, in line with commercial prescription;
• Signature integrity must remain verifiable throughout the retention period, which requires using signature formats with guaranteed longevity (XAdES-B-LT or XAdES-B-LTA with qualified timestamping).

The qualified electronic timestamping plays a critical role here: it freezes the signature creation date 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

A non-compliant electronic invoice (absence of valid signature, non-approved format, missing data) exposes the company to:

• Rejection of VAT deductibility on corresponding purchases (article 272 CGI);
• Tax penalties of up to €15 per non-compliant invoice, with a minimum of €60 per transaction (article 1737 CGI);
• 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 enabling automation of invoice signing on the fly, directly from ERPs (SAP, Oracle, Sage, Cegid…) or invoicing platforms (Chorus Pro for public procurement, private PDPs for the private sector).

A typical workflow 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 XAdES-B-LT signature with the company's qualified certificate;
3. Transmission of the signed invoice to the PPF or PDP;
4. Automatic archiving 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 (QTSP) listed on the national trust list (TSL), published and maintained by ANSSI. Active QTSPs in 2026 include Certigna, ChamberSign, Certinomis, and European players like Qualified Trust Service Providers referenced in the European Trust List.

Certificates are issued after identity verification of the legal representative or authorised signatory, face-to-face or by video identification depending on providers. Standard validity duration 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 vs signature: a distinction not to be overlooked

In the context of automated invoicing, an important technical distinction must be made: electronic signature (commitment of an identified natural person) and electronic seal (commitment of a legal person, 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 individual signer intervention at each invoice. DGFiP recognises both methods provided the underlying certificate is qualified under 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.

Legal framework applicable to signed electronic invoices

Compliance with signed electronic invoices rests on a stack of regulatory texts that it is essential to master.

Civil Code, articles 1366 and 1367: article 1366 establishes the principle of equivalence between electronic writing and paper writing, provided that the identity of the person from whom it originates is duly assured and that the document is drawn up and kept in conditions likely to guarantee its integrity. Article 1367 defines electronic signature as the use of a reliable identification process guaranteeing its link with the document to which it is attached.

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), 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), progressively entering into force since 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 three routes to compliance for electronic invoices (advanced electronic signature with qualified certificate, fiscal EDI, reliable audit trail). Article 289 bis clarifies the procedures applicable to EDI. Article 242 nonies A of Annex II lists the 25 mandatory mentions of an invoice, several of which are now transmitted electronically to DGFiP via the PPF.

Tax Procedure Book, article L102 B: requires retention of supporting documents for 6 years from the date they were drawn up or received. For invoices, professionals recommend retention of 10 years in line with commercial prescription periods (article L110-4 of the Commercial Code).

Order No. 2021-1190 of 15 September 2021 and implementing decrees: establish the progressive obligation for electronic invoicing for entities subject to VAT established in France, with deadlines deployed between 2026 and 2027 depending on company size.

ETSI EN 319 132 (XAdES) and EN 319 122 (CAdES) standards: European technical standards defining formats for advanced electronic signature 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 (name of individual customer, contact data) is subject to principles of minimisation, security and limitation of retention duration. Electronic signature also involves processing of signatory identity data, governed by GDPR and certification policies of QTSPs.

Legal and tax risks: an electronic invoice whose signature is invalid, expired or produced with a non-qualified certificate can 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 signature of invoices in practice

Scenario 1: an industrial SME with high volume of supplier invoicing

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

By deploying an electronic 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 the payment cycle from 45 to 18 days (-60%), zero VAT rejection during the next tax audit, and estimated savings of 35% on administrative invoice processing costs (range consistent with Gartner 2025 sector benchmarks on accounting dematerialisation).

Scenario 2: an accounting firm managing invoicing for 80 SME/micro-enterprise clients

An accounting firm of about fifteen employees, mandated to manage accounting and produce invoices for its client companies, had to ensure 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 enabling management of a portfolio of qualified certificates per client, with complete signature traceability and automatic archiving in individual digital safes. Estimated time savings: 4 to 6 hours per month per client on manual validation and archiving tasks, representing potential of 320 to 480 hours freed annually for the firm, reallocated to higher-value missions (tax consulting, strategic support).

Scenario 3: a digital services company responding to public procurement tenders

A software services company of about a hundred employees, operating mainly with public sector clients via Chorus Pro, had to ensure that each of its issued invoices complied with qualified electronic signature requirements imposed by certain public buyers.

By connecting its electronic signature solution to its invoicing tool via REST API, the company now automatically generates invoices in Factur-X format signed with qualified electronic seal, transmitted directly to Chorus Pro. Compliance is verifiable in real time by the buyer. No rejections for technical non-compliance have been recorded since production launch, compared to 3-4 rejections quarterly previously due to format errors or absence of valid signature. This approach fully aligns 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 topic reserved for IT departments: they are now at the heart of tax and accounting obligations for any company 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 issuer authenticity, data integrity and tax acceptability of invoices — whilst reducing processing times and audit risk.

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