Are Electronic Signatures Legal in Mexico? Three Different Things Go by That Name

This page quotes what the statutes actually say, with a link to each official source so you can check any statement yourself. It explains the law in general terms — it is not legal advice and cannot tell you how the law applies to your document. For that, ask a lawyer.

The question “are electronic signatures legal in Mexico?” is already answered, with the articles quoted in full, in are electronic signatures legally binding? The short answer is yes. This page answers the question that comes immediately afterwards, and that almost nobody separates properly.

Three different things are called “firma electrónica” in Mexico

Nearly everything published on the subject blends three figures that Mexican law keeps apart. The practical consequence is expensive: companies that believe they need a SAT certificate to sign a contract with a supplier, and companies that believe holding an e.firma settles the evidence for a commercial contract. Neither is true.

1. The Firma Electrónica of the Código de Comercio

This is the one that makes a contract between private parties binding. Article 89 of the Código de Comercio defines it:

“Firma Electrónica: Data in electronic form recorded in a Data Message, or attached to or logically associated with it by any technology, used to identify the Signatory in relation to the Data Message and to indicate that the Signatory approves the information contained in the Data Message, and which produces the same legal effects as a handwritten signature, being admissible as evidence in court.”

No certificate appears there, no authority and no procedure. The same article 89 opens the Title with the principles governing its interpretation — “technological neutrality, party autonomy, international compatibility and functional equivalence” — and fixes its reach: the provisions of that Title “shall govern throughout the Mexican Republic in matters of a commercial nature.”

2. The advanced electronic signature issued by the SAT (the one known as “e.firma”)

This is a certificate, and it exists for dealing with the tax authority. Article 17-D of the Código Fiscal de la Federación opens by fixing exactly when it is required:

“When tax provisions require documents to be filed, those documents must be digital and must contain an advanced electronic signature of the author, except in cases where a different rule is established.”

That first sentence is the whole boundary. The obligation arises from tax provisions, and it answers to them. The same article says who issues the certificate: the Servicio de Administración Tributaria “in the case of legal persons”, and “a certification service provider authorised by the Banco de México in the case of individuals.” And it states the effect: “an advanced electronic signature covered by a valid certificate shall replace the signatory’s handwritten signature, shall guarantee the integrity of the document and shall produce the same effects that the laws grant to documents bearing a handwritten signature, having the same evidentiary value.”

One detail helps untangle the knot: the word “e.firma” does not appear in the law. Not in the Código Fiscal, not in the Código de Comercio, not in the Ley de Firma Electrónica Avanzada. It is the commercial name by which the certificate is known; the legal text always says firma electrónica avanzada. That the colloquial name of a tax certificate so closely resembles the Código de Comercio’s term is, in large part, where the confusion comes from.

The Ley de Firma Electrónica Avanzada is the third piece of the same misunderstanding, and its own article 4 draws the boundary:

“Article 4. The provisions of this Law shall not apply to acts in which the use of the advanced electronic signature is not feasible by provision of law, or to those in which there is a prior opinion of the Ministry. Nor shall they apply to tax, customs and financial matters.

In acts of commerce and registrations in the Public Registry of Commerce, the use of the advanced electronic signature shall be governed in accordance with the provisions of the Código de Comercio and other applicable rules in the field, without prejudice to the application of the provisions of this Law to the extent appropriate.”

It is worth reading that second paragraph to the end, because the clause usually cut — “without prejudice to the application of the provisions of this Law to the extent appropriate” — qualifies the referral rather than making it absolute: in acts of commerce the Código de Comercio governs, and the Ley de Firma Electrónica Avanzada is not entirely out of the picture. Its own field, per article 2, section I, is acts in which private parties and public servants “of the agencies and entities of the Federal Public Administration, and of the administrative units of the Office of the President” use the advanced electronic signature. It is the law for dealing with the federal government.

3. The “Advanced or Reliable” signature of article 97

This is the most misunderstood of the three, because it sounds like a product category and is not one. The Código de Comercio defines it by referring to a test: “Firma Electrónica Avanzada o Fiable: that Electronic Signature which meets the requirements contemplated in sections I to IV of article 97.” And article 97 sets those requirements:

“The Electronic Signature shall be considered Advanced or Reliable if it meets at least the following requirements:

I. The Signature Creation Data, in the context in which they are used, correspond exclusively to the Signatory;

II. The Signature Creation Data were, at the time of signing, under the exclusive control of the Signatory;

III. It is possible to detect any alteration of the Electronic Signature made after the moment of signing, and

IV. With respect to the integrity of the information in a Data Message, it is possible to detect any alteration of it made after the moment of signing.”

And it closes by leaving the door open in both directions: “The provisions of this article shall be understood without prejudice to the possibility that any person may demonstrate in any other manner the reliability of an Electronic Signature; or present evidence that an Electronic Signature is not reliable.”

Read that twice. It does not say the advanced signature is valid and the simple one is not: article 97 itself begins by stating that the signature requirement is satisfied “if an Electronic Signature is used that is appropriate for the purposes for which the Data Message was generated or communicated.” Reliability is proved — or destroyed — with evidence. It is a step in evidence, not in validity, and no commercial label confers it.

Which of the three your document needs

• A contract, a purchase order, an NDA, a lease or an offer letter between private parties. The first. You need no e.firma and no certificate of any kind. What is worth having is what article 97 asks you to demonstrate if someone disputes it: exclusive control of the creation data, and the ability to detect any later alteration.
• Tax returns, invoicing, filings and any document a tax provision asks you for. The second, by command of article 17-D. And there is no alternative there: it is the certificate or nothing.
• Procedures before agencies of the Federal Public Administration. The field of the Ley de Firma Electrónica Avanzada, article 2, section I.
• A document you expect to end up in litigation. The third matters, but not as a purchase: it matters as the list of what you will have to be able to prove. That is the point of the validity-versus-evidence distinction that closes are electronic signatures legally binding?

Commercial or civil: the jurisdiction question that does matter

There is a second prior question, and it is the only allocation-of-competence question that changes anything in practice: whether your act is commercial or civil.

If it is commercial, the rule is federal and uniform. Article 1 of the Código de Comercio is categorical: “Commercial acts shall be governed solely by the provisions of this Code and the other applicable commercial laws.” And the electronic commerce Title governs “throughout the Mexican Republic in matters of a commercial nature.” Most business contracts are acts of commerce, so for most readers of this page the answer is the same in all 32 states, and there is nothing to check state by state.

If it is civil, competence is state-level. Each federal entity has its own civil code, and the Código Civil Federal governs in the federal sphere. The equivalent provisions are widely generalised, but the applicable text is your state’s. The federal reference articles — 1803 on express consent by electronic means, 1832 on the absence of required formalities, and 1834 bis on integrity, attribution and accessibility — are quoted in full in are electronic signatures legally binding?

This is a substantive difference from countries such as Canada, where the ordinary commercial contract falls under provincial law and the exclusions vary from province to province: there you almost always have to look at the local statute, and we break that down in are electronic signatures legal in Canada? In Mexico, for the typical commercial contract, you do not.

What to check before you e-sign in Mexico

1. Whether the act is commercial or civil. It decides whether the law governing you is federal and uniform or your state’s.
2. Whether a tax provision requires the document. That is the boundary of article 17-D, and the only situation in which the SAT certificate is mandatory.
3. Whether the law requires the act to be executed before a fedatario público. Where it does, it still does — though the third paragraph of article 93 allows you to reach the notary by data messages. We cover it in does an electronic signature need a witness or notary?
4. What you will be able to prove if the signature is challenged. The four sections of article 97 are, in practice, your requirements list for a provider: exclusive control of the creation data, and alteration detection over both the signature and the document.
5. How long your documents are kept, and in what state. Article 49 of the Código de Comercio imposes on merchants a minimum of ten years for documents recording contracts, agreements or commitments.
6. That nobody sells you NOM-151 as though it were a signature. It is a retention and digitisation standard, not a signature standard, and no contract needs a constancia de conservación to be valid. The breakdown is on the general page.

Where Signatura fits

Signatura produces an electronic signature in the sense of article 89: data logically associated with the document, identifying the signatory and indicating their approval. For a commercial contract between private parties that is exactly what the law asks for, and nothing more is needed.

On what article 97 would ask you to demonstrate, what we deliver is concrete: every completed document carries a full audit trail — who signed, when, from where and what they were shown — and a SHA-256 tamper-evident seal that makes any later alteration of the file detectable, re-verifiable at any time. That is what you need to be able to show if someone disputes reliability. The technical detail is on our security page, and the price — one plan per seat with unlimited documents — on our pricing page. Which Mexican platforms sell what, and at what published price in pesos, is in e-signature in Mexico.

Where Signatura is not the answer, stated plainly: we are not a Prestador de Servicios de Certificación accredited before the Secretaría de Economía, and we do not issue certificates. If what you need is the advanced electronic signature to satisfy a tax obligation, that is obtained from the SAT or from a provider authorised by the Banco de México, and we substitute for neither.

Frequently asked questions

Do I need the SAT’s e.firma to sign a contract with a customer?

No. The certificate known as e.firma exists for the tax sphere: article 17-D of the Código Fiscal requires it “when tax provisions require documents to be filed”. A contract between private parties is not that. In commercial matters, the Firma Electrónica of article 89 of the Código de Comercio produces “the same legal effects as a handwritten signature, being admissible as evidence in court”, and the definition mentions no certificate at all. What you may want to be able to prove afterwards is a separate matter, and that is what article 97 is about.

What is the difference between a simple and an advanced electronic signature in Mexico?

It is not a difference of validity but of evidence. Article 97 of the Código de Comercio treats a signature as “Advanced or Reliable” when the creation data correspond exclusively to the signatory and were under their exclusive control at the moment of signing, and when any later alteration of both the signature and the document can be detected. That same article begins by saying the signature requirement is met by an electronic signature “appropriate for the purposes for which the Data Message was generated or communicated”, and ends by allowing anyone to prove reliability “in any other manner” or to prove that a signature is not reliable. It is an evidentiary standard argued with evidence, not a label you buy.

Is the Ley de Firma Electrónica Avanzada Mexico’s general e-signature law?

No, and it says so itself. Its article 2, section I, limits the acts to those in which private parties and public servants “of the agencies and entities of the Federal Public Administration, and of the administrative units of the Office of the President” use the advanced electronic signature. Its article 4 additionally excludes “tax, customs and financial matters” and refers acts of commerce to the Código de Comercio, “without prejudice to the application of the provisions of this Law to the extent appropriate”. It is the law for dealing with the federal government, not the one that makes a contract between private parties binding.

Does the answer change from state to state?

For a commercial contract, no: article 1 of the Código de Comercio subjects commercial acts to that Code and to commercial laws, and the electronic commerce Title governs “throughout the Mexican Republic in matters of a commercial nature”. For a civil act it can change, because civil matters are the competence of each federal entity and each has its own code, although the equivalent provisions are widely generalised. The first question, then, is not which state you are in, but whether your act is commercial or civil.

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Sources: Código de Comercio (last reform DOF 14-11-2025) — article 1 on the scope of commercial acts; article 89 on reach “throughout the Mexican Republic in matters of a commercial nature”, the principles of technological neutrality, party autonomy, international compatibility and functional equivalence, and the definitions of “Firma Electrónica” and “Firma Electrónica Avanzada o Fiable”; article 93 on written form, signature and the electronic route to a fedatario público; article 97 with its sections I to IV and its closing paragraph; article 49 on ten-year retention. Código Fiscal de la Federación (last reform DOF 09-04-2026) — article 17-D on when the advanced electronic signature is required, who issues the certificate and what effect it produces. Ley de Firma Electrónica Avanzada (last reform DOF 14-11-2025) — article 2, section I, on its field, and article 4 in full on its exclusions and the referral to the Código de Comercio. The expression “e.firma” appears in none of the three texts: it is the certificate’s commercial name, and the law always says firma electrónica avanzada. Quotations have been translated from the Spanish originals linked above. This page explains the law in general terms and is not legal advice.