Electronic signatures in Mexico: the Commercial Code, e.firma and NOM-151

Electronic signatures are a normal part of doing business in Mexico, from supplier agreements to service contracts. The legal picture has a few moving parts, though: commercial law, civil law, a separate law for the advanced electronic signature used with authorities, and a technical standard on keeping electronic records. This guide walks through the essentials.

For a comparison with other countries, see our e-signature legality overview and the guide Are electronic signatures legal around the world?.

Are electronic signatures legal in Mexico?#

Yes, for most commercial and civil agreements. The main sources are:

• The Commercial Code (Código de Comercio). Its chapter on electronic commerce, added through reforms in 2000 and 2003, recognises data messages and electronic signatures in commercial dealings. Under certain conditions, a data message can meet a legal requirement for written form, and an electronic signature can meet a requirement for a signature.
• The Federal Civil Code (Código Civil Federal). It accepts that consent can be expressed by electronic means and sets out when an electronic document can meet a written-form requirement.
• The Advanced Electronic Signature Law (Ley de Firma Electrónica Avanzada, 2012). This law governs the use of the advanced electronic signature in dealings with federal public bodies.

Most private contracts in Mexico don't need any particular form, so a simple electronic signature can be used, and its value in a dispute will depend on the evidence behind it.

Types of electronic signatures recognised#

Mexican law broadly distinguishes two levels:

• Electronic signature (firma electrónica). Data in electronic form attached to or associated with a data message that can identify the signer and show their approval of the content. A typed name, a drawn signature or a click accepting terms can fall into this category.
• Advanced or reliable electronic signature (firma electrónica avanzada o fiable). A signature that meets extra requirements, such as being under the signer's sole control and making later changes detectable. In practice it is certificate-based. The best-known example is the e.firma (formerly FIEL) issued by the tax authority, SAT, which is used for tax filings and many government procedures.

The NOM-151-SCFI-2016 standard deals with preserving data messages. Many businesses obtain a NOM-151 preservation certificate (constancia de conservación) from an accredited certification service provider for documents they expect to rely on in court. Signkoi's trusted timestamp and audit trail aren't a NOM-151 certificate, so if you need one, plan for it separately.

Documents that often still need wet ink, a notary or a certified signature#

Some acts must follow a specific formality. Well-known examples include:

• Acts that must be formalised before a notary public (notario público), such as the sale of real estate and certain corporate acts.
• Wills, which are usually made before a notary.
• Marriage, divorce, adoption and other family matters handled by courts or the civil registry.
• Many filings and procedures with authorities, which require the e.firma or another advanced electronic signature.
• Negotiable instruments such as promissory notes (pagarés), which raise their own legal questions. Get advice before signing them electronically.

Collecting good evidence with simple e-signatures#

When a simple electronic signature is challenged, the court looks at the evidence: who signed, whether they agreed, and whether the document is unchanged. With Signkoi, every completed document includes:

• A deliberate signing step. Each signer draws, types or uploads a signature and agrees to sign electronically.
• A sealed PDF. A tamper-evident seal and a trusted timestamp make later changes detectable.
• An audit trail. Sending, opening and signing events are logged with times, IP addresses and browser details, and summarised in a certificate of completion.
• Optional identity checks. Ask signers to enter an access code you share separately, or a one-time code sent to their email.
• Independent verification. Anyone holding the PDF can check it at signkoi.com/verify.

Signkoi provides simple electronic signatures with strong evidence. It doesn't issue advanced electronic signatures or the e.firma, and it doesn't replace a notary.

How to send a document for signature in Mexico with Signkoi#

1. Upload your PDF, or start from a template.
2. Add your signers and set a signing order if needed.
3. Place signature and other fields for each signer.
4. Set reminders, an expiry date and, for important documents, an access code or email one-time code.
5. Send. Recipients sign in their browser with no account, and Signkoi's interface is available in Spanish, among 12 languages.
6. Download the sealed PDF and certificate of completion and store them with your records.

Frequently asked questions#

Do I need the e.firma to sign a contract with another company?#

Usually not. The e.firma is mainly used with SAT and other authorities. Private commercial contracts can generally be signed with a simple electronic signature, unless the law or the parties require a particular form.

Is a NOM-151 certificate mandatory?#

Not for every contract. NOM-151 sets rules for preserving data messages, and a preservation certificate can strengthen evidence. Some laws and businesses expect it for certain records, so check whether it applies to your documents.

Can a real-estate purchase be signed electronically?#

Preliminary documents such as offers or promise-to-sell agreements are sometimes signed electronically, but the transfer of real estate generally has to be formalised before a notary public.

Not legal advice#

This guide is general information, not legal advice. Laws change and may apply differently to your situation, and using Signkoi doesn't guarantee that a particular signature will be valid or enforceable. For important or regulated documents, talk to a qualified Mexican lawyer.