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Can Email and Chat Replace a Written Contract?

13 min readFLAT LAW FIRM
Sổ tay và bút — minh họa giá trị pháp lý của email, tin nhắn trong giao dịch

In daily business, plenty of deals are "closed" with a chain of back-and-forth emails or a few Zalo messages: the buyer sends a purchase order, the seller replies "OK, confirmed", and both sides start performing without signing any paper document. When a dispute erupts, the first question is always: do such emails and chats count as a contract, and can they replace a written contract?

The short answer is: yes, in most cases — Vietnamese law has long recognised electronic transactions, and the 2023 Law on Electronic Transactions (effective 01/7/2024) reinforces the principle. But "most" does not mean "all", and the legal value of an email or chat chain depends heavily on how the enterprise creates, stores and proves it.

This article answers the 9 questions FLAT Law Firm's clients ask most about using email and chat in place of written contracts, with specific legal bases and practical guidance to protect enterprises.

Contents

1. Can email and chat replace a written contract?

Short answer: Yes, for most ordinary commercial and civil transactions. Email and chat messages are treated by law as written form, so in principle they can replace paper contracts.

Explanation: The legal foundation rests on two key provisions. First, Article 119(1) of the 2015 Civil Code states plainly: civil transactions conducted via electronic means in the form of data messages under electronic-transaction law are deemed written transactions. Second, Article 9 of the 2023 Law on Electronic Transactions confirms that a data message has the value of a written document if the information it contains is accessible and usable for reference. In other words, the law does not discriminate between "ink on paper" and "text on screen" — what matters is the parties' contents and intent, not the medium.

For sale-of-goods contracts, Article 24 of the 2005 Commercial Law goes further: a contract may be expressed orally, in writing, or established by specific acts. Email and chat fall into the "written" group under the above reading, so closing an order by email is fully capable of forming a valid sale contract.

Legal basis: Article 119(1) of the 2015 Civil Code; Article 9 of the 2023 Law on Electronic Transactions; Article 24 of the 2005 Commercial Law.

Next steps: There is, however, one important exception: transactions that sectoral laws require to be notarised, certified or registered cannot be replaced by ordinary email or chat. See question 3. Enterprises should also distinguish this "contract formation" question from "what evidentiary value does email have in a dispute" — two different issues analysed in depth in questions 6 and 7.

2. Conditions for email and chat to count as a valid contract

Short answer: The email or chat chain must fully satisfy the validity conditions for civil transactions: lawful parties, fully voluntary consent, contents not violating legal prohibitions or social ethics — and must show a clear offer and acceptance with basic terms.

Explanation: The electronic form only answers "expressed how"; the "valid or not" question still follows Article 117 of the 2015 Civil Code like any other transaction. In practice, disputes over email/chat contracts rarely turn on the electronic form — they usually fall into three groups.

First, the parties: whether the sender had authority to represent the enterprise. An email from a sales employee's personal address, without authorisation, will struggle to bind the company. By contrast, an email from the enterprise's official domain, sent by the legal representative or an authorised person, carries entirely different weight.

Second, complete contents: the exchange must show a "contract offer" and "acceptance of the offer" with basic contents — subject matter, price, quantity, term, performance method. A price-inquiry email and a quotation reply are not yet a contract; but when the buyer sends a detailed purchase order and the seller replies confirming full agreement, the contract is concluded.

Third, voluntariness and lawful contents: the parties must be fully voluntary, and contents must not violate legal prohibitions or social ethics. This is a general condition for every transaction form.

Legal basis: Articles 117 and 119 of the 2015 Civil Code; Article 36 of the 2023 Law on Electronic Transactions on electronic contracting principles.

Next steps: Enterprises should issue internal rules clearly identifying who may conclude transactions via email or chat and through which addresses and accounts — the most effective preventive measure against authority disputes (see question 9).

3. Which transactions must still be made in paper writing?

Short answer: Transactions that sectoral laws require to be in notarised or certified writing, or to be registered, cannot be replaced by ordinary email or chat alone.

Explanation: Article 119(2) of the 2015 Civil Code sets a clear limit: where the law requires a civil transaction to be expressed in notarised or certified writing, or registered, that requirement must be followed. Typical cases in business practice include:

  • Land-use-right transfer and residential purchase contracts: must be notarised or certified under the 2024 Land Law and the 2023 Housing Law. An email agreeing on price counts only as a deposit agreement or memorandum — it cannot replace the transfer contract for title transfer.
  • Asset mortgage contracts: must be registered as secured transactions to take effect against third parties.
  • Some specialised transactions: bank credit contracts on mandatory forms, labour contracts in some cases, dealings with state agencies requiring paper files or digital signatures under sectoral rules.

Note that even in these cases, prior email and chat exchanges still have value: they evidence the negotiation process and the parties' intent, and can ground the resolution of disputes over deposits, deposit penalties or compensation when one side withdraws.

Legal basis: Article 119(2) of the 2015 Civil Code; the 2024 Land Law; the 2023 Housing Law.

Next steps: Before closing any high-value deal by email, check whether that transaction type falls under mandatory notarisation, certification or registration. In doubt, have a lawyer review the mandatory form before proceeding.

4. Is closing a deal over Zalo, Messenger or Viber legally valid?

Short answer: Yes, if the chat account is proven to belong to an authorised person of the counterparty, the contents show a complete offer and acceptance, and the chat data remains intact and retrievable. The biggest weakness of OTT chat is identifying the account holder.

Explanation: Legally, Zalo, Messenger and Viber messages are also data messages, treated like email under the 2023 Law on Electronic Transactions. The problem is not technology but proof. Corporate email is usually tied to an official domain with server-side storage, making sender identification relatively straightforward. A Zalo or Messenger account, by contrast, may be registered with a personal phone number, an arbitrary avatar, and contents that can be recalled or deleted — leaving the disputing party struggling to prove "the person I chatted with was the counterparty's representative".

In adjudication practice, courts typically assess the chat chain together with supporting evidence: whether the parties partially performed per the chat contents, whether a confirmation email followed the chat, whether the parties' statements align. A chat chain after which both sides delivered goods and paid exactly as chatted is highly persuasive, even without any signed paper.

Legal basis: Articles 12 and 14 of the 2023 Law on Electronic Transactions; Article 119(1) of the 2015 Civil Code.

Next steps: The golden rule for closing deals over chat: immediately after agreeing key terms on Zalo or Messenger, send a summary email confirming all terms and ask the other side to reply in agreement by email. That email becomes the evidentiary "anchor" for the whole chat chain.

5. Is an order-confirmation email or purchase order a contract?

Short answer: It can be a contract, if the email contains all elements of an acceptance of a contract offer. When offer and acceptance match, the contract is deemed concluded from the time of conclusion.

Explanation: In commerce the process usually runs: the buyer sends a purchase order stating goods, quantity, unit price, delivery term and payment conditions — this is the "contract offer". The seller replies "order confirmed, all terms agreed" — this is the "acceptance of the offer". When the two wills meet, the contract forms and takes effect from the time of conclusion under Article 401 of the 2015 Civil Code, unless the parties agree otherwise.

Two situations must be distinguished. If the seller's confirmation email modifies or supplements the purchase order's terms (e.g. changing the delivery date, raising the price), it is no longer an acceptance but a new offer — the contract forms only when the buyer confirms again. If the purchase order or email contains a clause that "this contract takes effect only when both sides sign a paper document", the confirmation email does not yet create a contract; that is the parties' agreement and must be respected.

Legal basis: Article 401 of the 2015 Civil Code; the Civil Code provisions on contract offers and acceptances.

Next steps: Enterprises should standardise purchase-order and order-confirmation email templates stating plainly that the confirmation email constitutes acceptance and when the contract takes effect. This eliminates arguments over "it was only discussion, not a contract".

6. How do I prove an email or chat came from the counterparty?

Short answer: Rely on Article 14 of the 2023 Law on Electronic Transactions on data message originators, combined with a supporting evidence system: the official domain, transaction history, digital signatures, and integrity-assured storage.

Explanation: Article 14 of the 2023 Law on Electronic Transactions provides: a data message is deemed to be the originator's if sent by the originator, their representative, or an information system set up to operate automatically as designated by the originator. That sets the legal framework, but in proceedings the relying party must still adduce specific evidence. Highly persuasive evidence types include:

  • An email address on the counterparty enterprise's official domain (e.g. name@company-domain), rather than a personal free email;
  • A consistent transaction history: the parties exchanged via the same email address or chat account over a long period and completed prior transactions;
  • Digital signatures on emails or electronic documents — the strongest evidence of identity;
  • Standards-compliant storage under Article 13 of the 2023 Law on Electronic Transactions: information accessible for reference, stored in its original format, with identifiable origin, sender, recipient and send/receive times;
  • Circumstantial evidence: the other side partially performed per the email/chat contents — performance is the most convincing admission that they are the transaction's party.

Legal basis: Articles 13 and 14 of the 2023 Law on Electronic Transactions.

Next steps: From the start of the trading relationship, establish "official channels" in writing: the parties agree on a list of authorised email addresses and accounts. That agreement belongs in the framework contract or the first working minutes.

7. What if one party denies having sent an email?

Short answer: The party relying on the email bears the burden of proving the counterparty originated it. The strongest measure is usually not technical forensics but proving the counterparty performed obligations under the email's contents.

Explanation: Denial of having sent an email is common in disputes. As a procedural principle, whoever makes the claim must prove it. The proof path typically runs from easy to hard.

First, technical evidence: extract email headers and server logs, and ask the email service provider to confirm. With corporate email on a private server system, this is relatively simple.

Second, forensics: where needed, digital forensics can determine the data message's origin and integrity.

Third, and usually decisive, is evidence of performance: if after that email chain the denying party delivered part of the goods, received a deposit, sent someone to inspect, or sent other emails or messages referencing the denied email's contents — the denial becomes unconvincing. Courts assess evidence comprehensively, not on a single piece.

Additionally, during proceedings the alleged sender may be required to testify, and testimony contradicting objective evidence works against them. Enterprises may also ask the court to apply timely electronic-evidence collection and preservation measures before data is deleted.

Legal basis: Article 14 of the 2023 Law on Electronic Transactions; the burden-of-proof principle in civil proceedings.

Next steps: At the first sign the counterparty may deny emails, preserve evidence immediately: back up the full email and chat chains in an authenticable format, record timestamps, and alter nothing. See also the analysis of the evidentiary value of email in contract disputes.

8. Do email or chat contracts need a digital signature?

Short answer: Not mandatory for most ordinary commercial and civil contracts. A digital signature strengthens confidence; it is not a general validity condition for electronic contracts.

Explanation: This is a common misunderstanding: many enterprises believe "without a digital signature, an email has no value". The law imposes no such requirement. Article 36 of the 2023 Law on Electronic Transactions sets out electronic contracting principles — the parties may agree to use data messages and electronic means in part or in whole for contracting and performance — without demanding digital signatures as a general mandatory condition.

Digital signatures work on two fronts: firmly identifying the signer and assuring content integrity after signing. So for high-value transactions, enterprises should absolutely use digital signatures as self-protection, even where the law does not require them.

The exception lies in specialised sectors where sub-law documents demand higher authentication. For example, electronic labour contracts under Decree 337/2025/ND-CP require identity authentication, digital signatures and timestamps; online dealings with state agencies have their own digital-signature and electronic-identification requirements. Enterprises in these sectors must follow sectoral rules.

Legal basis: Article 36 of the 2023 Law on Electronic Transactions; Decree 337/2025/ND-CP on electronic labour contracts.

Next steps: Assess by transaction value: ordinary deals can use confirmation emails; high-value or long-term deals should add digital signatures or a paper contract after closing terms by email. Learn more about electronic contracts and digital signatures.

9. How can enterprises maximise the evidentiary value of email and chat?

Short answer: Four things: internal rules on electronic-transaction authority; a summary confirmation email after each chat closing; integrity-assured, retrievable storage; and upgrading to paper or digitally-signed contracts for large deals.

Explanation: The legal value of email and chat is determined not only by law but by how the enterprise operates. Four practical measures, distilled from dispute-resolution experience:

One, internal electronic-transaction rules. State plainly who may close deals via email or chat; the list of authorised official email addresses and accounts; value limits per channel. These rules are both an internal governance tool and authority evidence in disputes.

Two, an "anchor" email after each chat closing. Right after agreeing key terms on Zalo, Messenger or Viber, send a summary email confirming all terms and ask the other side to reply in agreement. This minutes-long step creates clear documentary evidence, curing OTT chat's identity weakness.

Three, standards-compliant storage. Follow Article 13 of the 2023 Law on Electronic Transactions: store in the original format, keep accessible for reference, record origin, sender, recipient and times. Never delete or edit exchange chains. For important chats, export authenticated copies periodically.

Four, upgrade the form with transaction value. For high-value, long-term or complex deals, after closing terms by email the parties should sign a paper contract or a digitally-signed electronic contract. Not because email lacks value, but because prevention always costs less than disputes.

Legal basis: Article 13 of the 2023 Law on Electronic Transactions; practical contract-dispute experience.

Next steps: Review your order-closing and transaction-confirmation processes now: are there rules on who may close via email or chat, and how is the data stored?

Need a review of your electronic transactions?

Closing deals by email and chat is an irreversible practice, but how an enterprise organises it decides its ability to protect its rights when disputes arise. FLAT Law Firm helps enterprises build internal electronic-transaction rules, standardise order-confirmation email templates, and assess the evidentiary value of email and chat chains in ongoing disputes. Contact hotline 0988424851 for advice.

References

  1. Law on Electronic Transactions No. 20/2023/QH15, effective 01/7/2024.
  2. Civil Code No. 91/2015/QH13, effective 01/01/2017.
  3. Commercial Law No. 36/2005/QH11, effective 01/01/2006.
  4. Decree No. 337/2025/ND-CP on electronic labour contracts.