Is a Contract Signed by Email or WhatsApp Legally Valid? Understanding the Legal Effects of Electronic Signatures and Digital Communications

With the digital transformation of business relations, it has become common to formalize agreements through email, WhatsApp messages, management apps, or digital platforms. Faced with this reality, many wonder: is a contract made or accepted by electronic means legally valid? Moreover, can messages exchanged in messaging apps be used as evidence?

In this article, we explain what Brazilian law says about electronic signatures, the legal validity of digital contracts, and how to ensure security in agreements executed outside of paper.

1. What Does the Law Say About Contracts Signed by Digital Means?

Brazilian law recognizes the validity of electronic contracts, provided that the principles of party autonomy, good faith, freedom of form, and legal capacity are observed.

A signature does not need to be handwritten to produce legal effects. According to Article 104 of the Civil Code: “The validity of a legal transaction requires: (...) III – form prescribed or not prohibited by law.”

In other words: if the law does not require a specific form (such as a public deed), the contract may be valid even without a physical signature — including when executed by messages or emails.

In addition, Law No. 14.063/2020, which regulates electronic signatures, and the Brazilian Internet Act (Law No. 12.965/2014) reinforce the legality of digital documents and their acceptance as evidence in court.

2. Types of Electronic Signatures and Their Legal Effects

Brazilian legislation recognizes three types of electronic signatures, depending on their level of security:

Type of Signature	Characteristics	Legal Validity
Simple	Login, acceptance via email, WhatsApp, or click-to-accept	Valid, but requires proof of authorship and integrity
Advanced	Biometrics, token, geolocation, two-factor authentication	Valid, with stronger evidentiary force
Qualified (ICP-Brasil)	Digital certificate issued by an official authority	Equivalent to handwritten signature for legal purposes

e signature — such as acceptance by WhatsApp — may be legally valid, provided it is possible to prove:

·         Who sent the message;

·         The content accepted or agreed upon;

·         The integrity of the communication (no later alterations).

3. Contract by WhatsApp or Email: Is It Valid as Evidence?

Yes. Courts across Brazil have recognized WhatsApp conversations, emails, and screenshots as valid evidence, including for debt collection, contractual liability, and proof of business relationships.

·         “The exchange of electronic messages between the parties, via WhatsApp and email, proves the existence of a verbal contract with clear obligations.” (TJSP – Civil Appeal 1009281-14.2021.8.26.0002)

·         “Conversations conducted through messaging applications have probative value when not specifically contested by the opposing party.” (STJ – AgInt in AREsp 1.630.810/SP)

It is recommended to capture messages with date, time, and identification of the phone number or email in their entirety. Technical verification tools and even notarial certificates can reinforce the authenticity of the evidence.

4. Precautions When Entering Into Digital or Message-Based Contracts

Although valid, contracts entered into via email or WhatsApp must follow basic precautions to ensure legal security and avoid future disputes:

·         Clearly identify the parties involved: full name, CPF/CNPJ (tax ID), email or phone number, and each party’s role.

·         Record the object of the contract with clarity: avoid ambiguities about what is being contracted, deadlines, amounts, payment methods, termination conditions, etc.

·         Keep the conversation history saved and protected: preferably as a PDF or secure backup.

·         Avoid later modifications without express agreement: changes to the contract or its performance must be communicated and validated by both parties.

·         Whenever possible, formalize the final terms in a single document: even if the negotiation began by messages, the ideal is to consolidate it in a proposal, contract, or final email with express acceptance.

5. When Is a Physical or Qualified Digital Signature Mandatory?

Despite freedom of form, certain legal transactions require specific formalities, such as:

·         Purchase and sale of real estate worth more than 30 minimum wages (requires a public deed – Civil Code, Art. 108);

·         Suretyship or guarantee contracts (require express signature of the guarantor);

·         Corporate acts requiring registration in notary offices or commercial registries;

·         Powers of attorney with specific powers.

In these cases, a WhatsApp contract is not sufficient and must be complemented by formal execution.

6. Final Considerations

Yes, contracts executed by email or WhatsApp are legally valid in Brazil, provided the parties, the negotiation content, and the clear acceptance of obligations are identifiable. They may also be used as valid evidence in court, including for collection, damages, or termination purposes.

However, informality requires caution: the more complex or significant the legal relationship, the more advisable it is to adopt digital documents with advanced or certified signatures, in order to avoid disputes over the validity of the agreement.

Preventive legal counsel is essential for drafting, validating, or reviewing electronic contracts, ensuring legal security without losing agility in digital negotiations.