How to Sign a Digital Contract with SAT’s e.firma in Mexico

Digitalization has revolutionized how we handle legal documents. Nowadays, it’s possible to sign a contract without printing or scanning, saving time and resources. In Mexico, the SAT’s e.firma (electronic signature) is a crucial tool for digitally authenticating documents, ensuring their legal validity. In this article, we’ll teach you how to sign a digital contract with SAT’s e.firma in Mexico, the steps to follow, and the benefits of using this tool to streamline your processes.

What is SAT’s e.firma?

The e.firma, provided by the Tax Administration Service (SAT) in Mexico, is an advanced electronic signature with the same legal validity as a handwritten signature. With it, you can authenticate your identity in various online procedures and transactions, including the signing of digital contracts.

This tool makes signing contracts easier without the need for face-to-face meetings, improving efficiency and reducing costs. But how can you use it to sign a digital contract? Below, we explain the process step by step.

What Do You Need to Use the e.firma?

Before learning how to sign a digital contract with SAT’s e.firma, it’s essential to consider the following requirements:

  1. Active e.firma: If you don’t have an e.firma yet, you can request it on the SAT website or visit a SAT office to obtain it.
  2. e.firma Files: The e.firma consists of a .cer file (certificate), a .key file (private key), and a password.
  3. Digital Signature Platform: Various platforms allow you to sign digital documents using the e.firma, such as the SAT portal or services like Contractualis, a platform that enables you to sign contracts with e.firma easily.

Step by Step: How to Sign a Digital Contract with SAT’s e.firma in Mexico

Step 1: Prepare the Digital Contract

First, make sure your contract is in digital format. You can draft it in Word, Google Docs, or any text processor and save it as a PDF. Ensure that all the information is clear and ready to be signed.

Step 2: Upload the Contract to a Signature Platform

There are several platforms where you can sign digital contracts using SAT’s e.firma. One example is Contractualis, a solution designed to manage and sign legal documents efficiently and securely. Here, you can upload your contract and proceed with the digital signature.

Step 3: Enter Your e.firma Data

After uploading the contract, you will need to input your e.firma files (the .cer file, the .key file, and the password). These files authenticate your identity and apply your digital signature to the document.

Step 4: Sign the Document

Once you’ve provided your e.firma data, the platform will automatically apply your digital signature to the contract. This process takes just a few seconds, and your contract will be digitally signed.

Step 5: Share the Signed Contract

After signing, you can share the contract with the other parties involved. The digital signature with e.firma ensures that the contract hasn’t been altered and holds the same validity as a handwritten signature.

Benefits of Using SAT’s e.firma to Sign Digital Contracts

Using the e.firma from SAT to sign digital contracts in Mexico comes with numerous benefits:

  • Security and Authenticity: The e.firma ensures that the document cannot be modified after being signed, guaranteeing its integrity.
  • Legal Validity: Contracts signed digitally with the e.firma from SAT have the same legal validity as handwritten ones.
  • Efficiency: Digital signing saves time, eliminating the need to print, scan, or mail documents.
  • Accessibility: You can sign contracts from anywhere, all you need is access to your e.firma files and a compatible platform.
  • Sustainability: Reducing paper usage not only benefits your business but also helps the environment.

How Contractualis Helps Sign Contracts with e.firma

If you’re looking for an intuitive platform to manage and sign contracts digitally, Contractualis is an excellent choice. Not only does it allow you to sign documents quickly, but it also supports SAT’s e.firma, making it easy to sign contracts with full legal validity.

With Contractualis, you can upload your contract, sign it digitally with your e.firma, and share it with other parties without the need for printing or physical delivery. This makes Contractualis a comprehensive solution for businesses looking to streamline their legal processes.

What’s the Difference Between Digital Signature and Electronic Signature?

It’s common to confuse digital signatures with electronic signatures, but they’re not the same. If you’d like to know more about the differences between these two types of signatures, we recommend reading this article: Digital Signature vs Electronic Signature.

This article explains in detail the characteristics and differences between both types of signatures, helping you decide which is suitable for each situation.


Learning how to sign a digital contract with SAT’s e.firma in Mexico is essential for any business or professional looking to optimize their legal processes. The e.firma from SAT allows you to sign contracts securely, quickly, and with full legal validity, eliminating the barriers of traditional paperwork.

If you don’t have your e.firma yet, obtaining it through the SAT portal is the first step to start benefiting from its advantages. And if you already have it, Contractualis is the ideal platform to manage and sign your digital contracts.

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