Electronic Invoices with Digital Signatures: Tax Compliance 2026

Dematerialisation of invoices is no longer optional: since the progressive entry into force of the obligation to issue electronic invoices in France, introduced by Ordinance No. 2021-1190 of 15 September 2021 and subsequent implementing decrees, enterprises 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, a guarantee of authenticity, integrity and tax compliance. This article explores the accepted formats, legal obligations, required signature levels and best practices to secure your processes in 2026.

Why digital signature is at the heart of electronic invoicing

The Direction Générale des Finances Publiques (DGFiP) imposes three cumulative conditions for an electronic invoice to be fiscally acceptable: the authenticity of the origin, the integrity of the content and the legibility of the document (article 289 of the French General Tax Code). Advanced or qualified electronic signature is 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 Code général des impôts, 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 mutual authentication protocols;
• Reliable audit trail, which requires complete process documentation, often costly to maintain for SMEs.

For the vast majority of enterprises, digital signature on approved XML formats remains the most legally robust solution and the most technically scalable. It integrates natively into dematerialised workflows 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 certainly 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. Time-stamping: the date and time of issuance are certified, which can prove decisive in the event of a tax or commercial dispute.

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

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 reference format

Factur-X (called ZUGFeRD in Germany) is a hybrid PDF/A-3 format integrating a structured XML file (conforming to EN 16931 standard). It is widely praised 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 depending on 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 European Directive 2014/55/EU;
• Extended profile: additional data for sectors with strong automation needs (distribution, industry).

UBL and CII: the 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 XAdES-B-LT (Long-Term) variant is recommended to guarantee the verifiability of the signature for the duration of 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, incontestable in the event of tax or commercial disputes, recommended for high-stakes invoices (public contracts, major accounts, intra-community operations).

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

Tax obligations: what the DGFiP actually controls

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

Mandatory data for a compliant electronic invoice

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

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

This data now flows to the administration via the PPF or PDPs. Electronic signature certifies that this data has not been altered between issuance 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 Code, article L102 B);
• 10 years in the practice recommended by chartered accountants, in line 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 fixes the date of signature creation and allows you to prove that the certificates used were valid at the time of signing, even if these certificates have since expired.

Risks in case of non-compliance

An electronic invoice that is non-compliant (absence of valid signature, unapproved format, missing data) exposes the company 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);
• 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 financial 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…) or invoicing platforms (Chorus Pro for public contracts, 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 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 (PSCQ) listed on the national trust list (TSL), published and maintained by ANSSI. Among active PSCQs in 2026: Certigna, ChamberSign, Certinomis, or even European actors such as Qualified Trust Service Providers listed in the European Trust List.

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

To compare the solutions available on the market and choose 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 neglected

In the context of automated invoicing, an important technical distinction arises: 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 flows, the 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 methods provided 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 persons.

Applicable legal framework for signed electronic invoices

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

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

Regulation eIDAS No. 910/2014 of the European Parliament and of the 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 applied since 2025, strengthens interoperability requirements and introduces the European digital identity wallet (EUDIW).

French General Tax Code, articles 289 and 289 bis: article 289 CGI establishes the three compliance routes for electronic invoices (advanced electronic signature with qualified certificate, fiscal EDI, reliable audit trail). Article 289 bis specifies the procedures applicable to EDI. Article 242 nonies A of Annex II lists the 25 mandatory invoice mentions, several of which are now electronically transmitted to the DGFiP via the PPF.

Tax Procedure Code, 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 French Commercial Code).

Ordinance No. 2021-1190 of 15 September 2021 and implementing decrees: establish the progressive obligation to issue electronic invoices for enterprises subject to VAT established in France, with deployment deadlines between 2026 and 2027 depending on company size.

ETSI EN 319 132 (XAdES) and EN 319 122 (CAdES) standards: 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 (name of individual customer, contact data) 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 PSCQ certification policies.

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

Use cases: digital signature of invoices in practice

Scenario 1: an industrial SME with high volume supplier invoicing

An industrial SME processing approximately 3,500 supplier invoices per year faced two recurring problems: delays in manual validation lengthening the payment cycle to 45 days on average, and occasional VAT deduction rejections 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 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 administrative invoice processing costs (range consistent with Gartner 2025 sectoral benchmarks on accounting dematerialisation).

Scenario 2: an accounting advisory firm managing invoicing for 80 SME/SMI clients

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

The firm opted for a multi-entity signature platform allowing management of a portfolio of qualified certificates per client, with full traceability of signatures 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 a potential of 320 to 480 hours freed annually for the firm, reallocated to high-value missions (tax advice, strategic support).

Scenario 3: a digital services company responding to public sector contracts

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

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 client. No rejections due to technical non-compliance have been recorded since production launch, against 3 to 4 quarterly rejections previously due to format errors or absence of valid signature. This type of approach fits fully within the 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 lasting compliance in 2026 and beyond.

Qualified digital signature simultaneously guarantees the authenticity of the issuer, the integrity of data and the tax acceptability of invoices — while reducing processing delays and audit adjustment risks.

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.