Mexico's e-signature framework rests on two pillars: the Código de Comercio and the Ley de Firma Electrónica Avanzada.

The Código de Comercio, reformed in 2000, 2003, and 2009, added Articles 89 through 114 bis to establish functional equivalence between electronic and paper documents, and between electronic and handwritten signatures. Article 89 sets the baseline: parties can use whatever technology they agree to, and courts can't deny legal effect to a document just because it's electronic.

Signature Types Recognized

Firma Electrónica Simple: Any electronic data that identifies the signer and shows their approval. Valid for most commercial contracts, with reliability argued case by case if challenged.

Firma Electrónica Avanzada (or Fiable): Meets the four-part test in Código de Comercio Article 97: the signature's creation data belongs exclusively to the signer, that data was under the signer's sole control at the moment of signing, and any later change to either the signature or the underlying message can be detected. Meeting this test gives the signature a statutory presumption of authenticity a Firma Electrónica Simple doesn't automatically carry.

This is a genuinely two-tier system, and it doesn't map onto the EU's SES, AES, and QES structure. Mexico has no third category above Advanced with its own separate legal presumption. The Ley de Firma Electrónica Avanzada, enacted in 2012, doesn't create a new signature level. It sets out how government agencies and SAT, Mexico's tax authority, implement the Advanced tier for their own purposes, most visibly through SAT's own e.firma. Private certification providers, called Prestadores de Servicios de Certificación, are accredited by the Secretaría de Economía and issue certificates that private parties can use to meet the Advanced test. That accreditation gives a signer one accepted route to Advanced status. It does not add a separate legal tier above it.

A 2023 reform to the General Law of Business Entities extended electronic signatures to corporate actions like shareholder resolutions, and the 2023 National Code of Civil and Family Procedure admits electronically signed documents as evidence on the same footing as paper. Together with the Código de Comercio's functional equivalence rule, this covers the large majority of commercial paperwork a SaaS company, agency, or internal team is likely to need signed.

The clearest recent wrinkle is a thesis published October 24, 2025 by Mexico City's Second Collegiate Circuit Court in Civil Matters, addressing what signature level a digital promissory note (pagaré) needs to function as an executable credit instrument. The court concluded that only an Advanced Electronic Signature satisfies that standard, leaning on NOM-151, the technical standard for preserving data messages, to justify the requirement. Commentators have pushed back on this reasoning: NOM-151 governs document preservation and time stamping, not signature attribution, and the ruling effectively reads a certification requirement into a law that never imposed one for private contracts generally. It's a circuit-level thesis. The Supreme Court hasn't ruled on the question, and it's worth tracking closely if your product issues or handles pagarés specifically.

For most SaaS companies, agencies, and internal teams operating in Mexico, a Firma Electrónica Simple or Advanced signature covers commercial contracts, employment agreements, NDAs, and software licenses without needing a notary, an accredited certificate, or SAT's own e.firma. Those requirements apply to a specific, named list of exceptions: wills, property transfers, civil-status filings, notarial acts, and now, per the contested 2025 thesis, digital promissory notes.