By Raúl Fernández, 1 Lilia Alonzo2 and Aldo A. Jáuregui3

We recently published an article regarding certain alternatives to traditional methods for signing commercial documents and closing business transactions on a remote basis (primarily due to the pandemic caused by COVID-19). We discussed the validity of electronic signatures, the different types of such signatures and their admissibility as evidence. Below we analyze these topics in more depth and discuss additional related matters, such as the possibility of setting a Certain Date (Fecha Cierta) to documents through an electronic signature with a digital time stamp.

I.  Valid to Express Consent

In accordance with Mexican law, the use of electronic signatures is a valid way to express consent for the execution of contracts. Specifically, the Federal Civil Code (Código Civil Federal) provides that consent will be express when it is manifested, among others, by electronic, optical or any other type of technology. In cases in which it is required that the consent be in writing, such requirement will be considered fulfilled when the electronic information is attributable to the obligated persons and can be subsequently consulted.4 The foregoing is endorsed by the Commercial Code (Código de Comercio).5

Principles of Interpretation

The Commercial Code provides that electronic commerce (e-commerce) will be interpreted and applied in accordance with the following guiding principles:6

  • Technological neutrality: the technology used for the issuance of digital certificates and for the provision of services related to the electronic signature shall be applied in such a way that does not exclude, restrict or favor any particular technology;7
  • Will autonomy: to the extent permitted by the applicable regulations, the parties shall be free to contract and express their consent in the way they agree;8
  • International compatibility: recognized international standards and criteria shall be used;9 and
  • Functional equivalence: the electronic signature on a data message shall satisfy the signature requirement in the same way as the wet signature on a printed document if it has the same level of reliability).10

These principles of interpretation are relevant to determine the way in which the electronic signature must be interpreted for legal purposes in commercial matters when used instead of a wet signature.

II.  Types of Electronic Signature

In line with the international trend, the Commercial Code identifies three types of electronic signatures:

1.  Simple electronic signature: the data in electronic form recorded by any technology in a data message, which indicates that the signatory approves the information contained in such data message.11

Common examples of this type of signature are digital wet signatures and personal identification numbers (PIN) used to authorize charges to a credit card. The use of biometric factors (fingerprint, voice or facial identifiers, among others) could also fall into this category.

2.  Advanced or reliable electronic signature: one that meets at least the following requirements:12

a)  the signature creation data, in the context in which it is used, corresponds exclusively to the signatory;

b)  the signature creation data was, at the time of signing, under the sole control of the signatory;

c)  it is possible to detect any alteration of the electronic signature made after the moment of signature; and

d)  regarding the integrity of the information in a data message, it is possible to detect any alteration of it made after the moment of signing.

This type of signatures may be issued by authorities or certification service providers (“CSP”).13 The most common example of this type of signature is that issued to those enrolled in the Federal Taxpayer Registry (Registro Federal de Contribuyentes) by the Tax Administration Service (Servicio de Administración Tributaria) ("SAT"). For foreigners who are not tax residents in Mexico it is common to obtain an advanced electronic signature from CSPs.

Certification Service Providers

CSPs are persons or public entities authorized by the Ministry of Economy (Secretaría de Economía) to issue certificates and/or provide related services such as (i) the preservation of data messages, (ii) the digital time stamp and (iii) the digitization of printed documents, according to the terms provided by the Official Mexican Standard on Digitization and Preservation of Data Messages (Norma Oficial Mexicana sobre Digitalización y Conservación de Mensajes de Datos) ("NOM-151").14

To date, the Ministry of Economy has authorized six private companies as CSPs, which are identified at Some of these companies have agreements with third parties who offer the electronic signature and other related services directly to the public (e.g., WeeSign, Mifiel, Firmamex or Doc2Sign).

The NOM-151 regulates the technical requirements under which CSPs may provide various services, including the issuance of (i) a digital certificate of electronic signature, which ties the identity of a person to an electronic document (for example, upon obtaining a certified advanced electronic signature from the SAT, the public entity delivers a file with the ".cer" file extension); and15 (ii) a time stamp, which demonstrates that the electronic document exists from and after a certain date and has not been altered.16

III.  Public Instruments

Mexican law requires a number of legal acts to be granted in a public instrument before a notary public or commercial broker. Common examples of these type of acts are the incorporation of commercial companies17 or trusts holding real estate,18 the formalization of minutes of extraordinary meetings,19 the ratification of signatures for non-possessory pledge agreements20 and certain powers of attorney.21 Notary publics and commercial brokers have been reluctant to allow the electronic signature of public deeds, despite the fact that the Commercial Code seems to allow it. 22

In any case, especially due to the COVID-19 pandemic, some notary publics and commercial brokers have agreed to formalize and ratify documents signed electronically (including shareholders' resolutions and non-possessory pledge agreements) to the extent the public instrument is still wet signed. A major backstop for notary publics and commercial brokers is the applicable law (i.e., local notary public laws and the Federal Law on Public Brokerage (Ley Federal de Correduría Pública), which may not regulate the use of electronic signatures, raising interpretation challenges.

IV.  Valid as Evidence

The Commercial Code provides that no legal effects, validity or binding effect shall be denied to any type of information for the sole reason that it is contained in a “Data Message”. Accordingly, such messages may be used as evidence in any proceeding before a legally recognized authority and shall have the same legal effects as wet signed documents.23 The Federal Code of Civil Procedures (Código Federal de Procedimientos Civiles) endorses the foregoing by providing that the information generated or communicated in electronic, optical or any other type of technology shall be recognized as evidence.24

In line with the above, when the law requires that the information is presented and preserved in its original form, that requirement may be satisfied with respect to a “Data Message” if (i) there is reliable evidence that the integrity of the information has been preserved and (ii) such information may be shown to its recipient. Likewise, the document shall be attributable to the parties.25

It should be clarified that, regardless of the type of signature used (simple or advanced, certified or not), the electronic signatures included in a "Data Message" may be contested in case of dispute (in the same way as wet signatures). In this case, the interested party will have to offer the relevant evidence in digital matters (e.g., instead of an expert in graphology, an expert in cryptography may be required).

V.  Certain Date (Fecha Cierta)

Taxpayers in Mexico, while facing tax verifications, have suffered from SAT dismissing their documents privately executed on the basis they lack of a “Certain Date” (Fecha Cierta). This conflict has been solved by the Supreme Court of Justice of the Nation (Suprema Corte de Justicia de la Nación) by confirming that SAT may require documents to have a “Certain Date”.26

The SCJN issued a criteria that provides that private documents acquire a Certain Date (i) from the date on which they are presented before a notary public or commercial broker, (ii) when they are registered in the Public Registry of Property (Registro Público de la Propiedad) or (iii) from the death of any of the signatories. However, we consider it possible to argue that, in addition to the three points above, the signing of documents using an advanced electronic signature with its respective digital time stamp may serve as evidence for such effects.27

VI.  International Transactions

Any certificate or electronic signature created or used outside of Mexico shall produce the same legal effects as a certificate or electronic signature created or used in Mexico if it has an equivalent degree of reliability. To determine such reliability, the international standards recognized by Mexico shall be taken into consideration (among others, the Model Law of the United Nations Commission on International Trade Law on Electronic Signature of 2001 ratified by Mexico in 2003), as well as any other relevant means of proof.28

Notwithstanding the foregoing, when the parties to a contract agree to use certain types of electronic signatures and certificates, such agreement shall be sufficient for purposes of cross-border recognition, unless such agreement is not valid or effective under applicable law.29

VII.  Platforms for Electronic Signature

Despite the fact that the regulation on electronic signature has existed for many years in Mexico, its use has not been wide spread and, to date, there are only a few companies that offer the electronic signature service and related services (time stamps, document digitization and/or preservation of data messages).

At Mayer Brown, having worked with and evaluated companies that provide electronic signature services and related services, we can advise clients considering using any of the various available services—and for any type of document—as well as using the platforms that offer such services.


2 See

3 See

4 Federal Civil Code. Articles 1803 and 1834 bis.

5 Code of Commerce. Articles 78, 79, 80 and 93.

6 Code of Commerce. Article 89.

7 UNCITRAL Model Law on Electronic Signatures. Article 3. Electronic Signature Law. Article 8. Section IV.

8 UNCITRAL Model Law on Electronic Signatures. Article 5.

9 UNCITRAL Model Law on Electronic Signatures. Article 7.

10 UNCITRAL Model Law on Electronic Signatures. Article 6. Electronic Signature Law. Article 8. Section I.

11 Code of Commerce. Article 89.

12 Code of Commerce. Article 97.

13 Code of Commerce. Article 98.

14 Code of Commerce. Articles 95 Bis 1, 95 Bis 3, 95 Bis 6, 100 and 102.

15 Code of Commerce. Article 104.

16 Code of Commerce. Article 101.

17 General Law on Commercial Companies. Article 5.

18 General Law on Negotiable Instruments and Credit Transactions. Articles 388 and 404.

19 General Law on Commercial Companies. Article 194.

20 General Law on Negotiable Instruments and Credit Transactions. Article 365.

21 Federal Civil Code. Article 2551.

22 Code of Commerce. Article 93.

23 Code of Commerce. Article 89 Bis.

24 Federal Code of Civil Procedures. Article 210 Bis.

25 Code of Commerce. Article 93 Bis. Federal Code of Civil Procedures.Article 210 Bis.

26 IUS. Jurisprudence thesis: 2a./J. 161/2019 (10a.) Second Section. Register number: 2021218.

27 Ídem.

28 Code of Commerce. Article 114.

29 Ídem.