How to enforce a contract when one party claims it wasn't signed

With the rise of digital transactions and remote negotiations, disputes over unsigned contracts are becoming increasingly common. Refusing to sign is sometimes used as a tactic to avoid responsibility. However, depending on the applicable law, required formalities, and available evidence, a contract may still be considered valid even without a signature if the parties clearly intended to be bound. In this article, we’ll explore when it is possible to enforce an unsigned contract, what evidence can prove mutual consent, which legal doctrines may apply, and what steps you can take to protect your rights.

Why are disputes over unsigned contracts a common problem in business?

Modern business relationships are increasingly conducted remotely. Negotiations often take place via messengers, terms are agreed upon through email, and files are exchanged using cloud services. In such a setting, the line between a “discussion” and a legally binding “agreement” can become blurred and a source of dispute. Companies frequently face situations where one party believes a deal has been reached, while the other refuses to perform, citing the absence of a signed contract.

These disputes are further complicated by differing legal standards across jurisdictions. In many legal systems, a contract may be formed without a handwritten signature if the parties have agreed on the essential terms and intended to create legal obligations. However, the result depends on the governing law, the type of transaction, any statutory form requirements, and the parties’ communications and conduct. In some cases, wording such as “subject to contract” or an express requirement for formal execution may show that the parties did not intend to be bound before signing.

Businesses that rely mainly on informal correspondence, verbal agreements, or fragmented approval processes may face greater evidentiary difficulties if a dispute arises. Without a clear record of acceptance, authority, and performance, it can become harder to claim payment, demand performance, or prove the existence and terms of an agreement in commercial litigation.

What makes a contract valid: understanding the legal structure?

To be legally enforceable in court, a contract must meet the basic requirements of legal validity. Even if an agreement is not formally signed, it can still be recognized as binding if the applicable law does not require a specific form and the parties’ intention to create legal obligations can be established.

Key elements of a valid contract

The requirements for contract formation depend on the governing law, but the following elements are commonly relevant:

1. Offer: one party makes a clear and specific proposal to agree to defined terms.
2. Acceptance: the other party accepts the offer in a manner recognised by the applicable law.
3. Consideration: in common law jurisdictions, each party generally provides something of value in return, such as money, goods, or services.
4. Intention to create legal relations: the circumstances indicate that the parties intended their agreement to have legal consequences.
5. Compliance with formal requirements: some categories of contracts must be in writing, signed, notarised, or executed in another prescribed form.

For example, if a supplier sends a commercial proposal, the client agrees on the price and delivery schedule, and partial payment is made, a court may recognize the contract as concluded even if no document was formally signed.

Is a signature required for a valid contract?

Not always. In many jurisdictions, a contract can be enforceable without a handwritten signature if the applicable law does not require one and there is sufficient evidence that the parties reached an agreement and intended to be bound.

Courts may consider email correspondence, electronic records, conduct, partial performance, invoices, payments, and other evidence of mutual assent. At the same time, specific transactions may be subject to statutory form requirements, so the absence of a required signature can affect enforceability.

Recent case: when emails can prove a contract

A useful recent example is Myers Water Transfer, LLC v. LOLA Energy PetroCo, LLC, decided by the Superior Court of Pennsylvania in December 2025. The dispute concerned a sale of used pipe where the parties negotiated and accepted key terms through email rather than executing a traditional signed contract.

The court found that the written communications and subsequent conduct demonstrated mutual assent. It also concluded that the emails satisfied the applicable Statute of Frauds requirements because the messages identified the company representatives by their names and positions and showed an intention to authenticate the communications. The case illustrates that an unsigned document does not automatically prevent enforcement where electronic correspondence and conduct clearly demonstrate agreement.

What evidence can confirm the existence of a contract?

When there is no signed document, the dispute usually comes down to evidence. Courts may look at the parties’ communications, conduct, payments, performance, and other records that show whether they actually reached an agreement and intended to be bound.

Emails and messages

Email correspondence, messages in corporate communication tools, and other written exchanges can help establish the agreed terms, acceptance, and the parties’ intention to proceed with the transaction. The strongest evidence usually comes from communications that clearly identify the parties, set out the essential terms, and show an unambiguous acceptance.

Where possible, businesses should preserve complete communication chains rather than isolated screenshots. Metadata, timestamps, sender details, attachments, and audit logs can also be important when authenticity or authorship is disputed.

Conduct and performance

A contract may also be inferred from the parties’ conduct. If one party starts delivering goods or services and the other accepts them, this may support the conclusion that an agreement existed even if no final document was signed.

Courts may consider:

• Delivery and acceptance of goods;
• Provision of services;
• Access granted to systems or platforms;
• Implementation of agreed commercial terms;
• Repeated performance consistent with the draft agreement.

Payments and invoices

Invoices, payment records, purchase orders, and bank transfers can also support the existence of a contract. They are particularly useful where payment descriptions, invoice references, or supporting correspondence link the transaction to specific agreed terms.

However, payment alone does not always prove the full content of the agreement. It should be assessed together with the surrounding communications and conduct.

Can chats and AI-generated agreements be used as evidence?

Yes, potentially. Messages exchanged through WhatsApp, Slack, Microsoft Teams, Telegram, or similar platforms may be relevant evidence if they can be authenticated and linked to the parties involved.

The same applies to AI-generated contract drafts. The fact that a document was created with an AI tool does not by itself make it binding or prove agreement. What matters is whether authorised representatives reviewed, accepted, or acted on the terms. Evidence of approval, subsequent performance, payment, or consistent communications may therefore be more important than the drafting method itself.

What legal doctrines apply if there is no signed contract?

Even without a signed agreement, a court may still protect the aggrieved party if certain legal doctrines apply. These principles are particularly relevant in common law jurisdictions, although their scope and requirements vary depending on the applicable law.

Implied-in-fact contract

An implied-in-fact contract may arise from the parties’ conduct even where no formal written agreement was signed. The key question is whether their actions objectively demonstrate mutual assent.

Relevant indicators may include:

• Negotiations followed by performance;
• Delivery and acceptance of goods or services;
• Payments made in accordance with agreed commercial terms;
• Conduct showing that both parties acted as if a binding agreement existed.

Unlike a purely equitable remedy, an implied-in-fact contract is based on the parties’ actual conduct and inferred intention to enter into a contractual relationship. Cornell’s Legal Information Institute similarly describes such contracts as agreements inferred from intentional conduct rather than expressly stated terms.

Promissory estoppel

Promissory estoppel may apply where one party reasonably relies on a clear promise and suffers a detriment because that promise is later withdrawn or not fulfilled.

Depending on the jurisdiction, relevant factors generally include:

• A sufficiently clear promise;
• Reasonable and foreseeable reliance on that promise;
• A resulting detriment;
• Circumstances in which enforcement or another remedy is necessary to avoid injustice.

Promissory estoppel may therefore become important where negotiations did not result in a formally executed contract, but one party materially changed its position in reliance on the other party’s promise.

Quantum meruit

Quantum meruit may allow a party to recover reasonable compensation for goods or services provided and accepted even where no enforceable contract can be established.

It should not be treated as proof that a contract necessarily existed. In many common law systems, quantum meruit operates as an equitable or restitutionary remedy designed to prevent unjust enrichment. The amount awarded generally reflects the reasonable value of the benefit or services provided rather than contractual damages under an established agreement.

How can you prove and enforce a contract if there is no signature?

If one party denies that a contract was concluded, the other party should first establish whether there is sufficient evidence of mutual agreement and performance. The strategy will depend on the applicable law, the available evidence, and any dispute resolution arrangements agreed between the parties.

1. Collect evidence

The first step is to preserve all records that may demonstrate the existence and terms of the agreement.

An evidence checklist for an unsigned contract may include:

• Emails, messenger conversations, and other correspondence;
• Contract drafts and tracked changes;
• Invoices, purchase orders, and payment records;
• Delivery notes, acceptance certificates, and other performance documents;
• Meeting minutes and written confirmations of agreed terms;
• Evidence of partial or full performance by either party;
• Internal approvals and corporate records;
• Electronic signature records, timestamps, and audit trails;
• Evidence identifying the representatives involved and their authority.

Evidence should be assessed as a whole. A single email or invoice may not establish all contractual terms, but several consistent records can provide a much stronger basis for proving mutual agreement.

2. Send a formal demand letter

Before initiating proceedings, it is often appropriate to send a formal demand letter setting out the claimant’s position.

The letter should:

• Identify the agreement and relevant obligations;
• Describe the breach or failure to perform;
• Refer to the available evidence of agreement;
• Demand performance, payment, or compensation;
• Specify a reasonable deadline for response;
• Explain what further legal action may follow.

A well-prepared demand letter can help resolve the dispute before formal proceedings and creates an additional written record of the claimant’s position.

3. Consider negotiation, mediation, or arbitration

Negotiation or mediation may allow the parties to resolve the dispute without litigation, particularly where preserving the commercial relationship is important.

If the parties agreed to an arbitration or other dispute resolution clause, that clause may determine how and where the dispute must be resolved. However, where the clause appears only in an unsigned draft, its enforceability should be assessed separately. The fact that a draft contains an arbitration clause does not automatically prove that both parties agreed to arbitrate.

For cross-border relationships, the choice between litigation, arbitration, mediation, and negotiation should also take into account the location of the parties and assets, enforceability of the eventual decision, costs, and applicable procedural rules.

4. Initiate court proceedings if necessary

If an out-of-court solution is not possible, the claimant may need to seek judicial enforcement.

Depending on the applicable law, it may be necessary to:

• Prove that the parties reached agreement on the essential terms;
• Demonstrate intention to create legal obligations;
• Provide evidence of performance or reliance;
• Establish the terms that were actually agreed;
• Explain why the absence of a signature does not prevent enforcement.

The court will assess the evidence, applicable contract law, mandatory formalities, and the parties’ conduct before deciding whether an enforceable agreement existed.

How to avoid such situations: practical recommendations for businesses

Disputes over unsigned contracts are easier to prevent than to resolve. Clear approval procedures, reliable electronic signing tools, and proper record-keeping help businesses demonstrate when an agreement was reached and who had authority to approve it.

Use written contracts whenever possible

A written contract should clearly set out the parties, key commercial terms, governing law, dispute resolution mechanism, and rules for amendments or termination. A clear contract amendment clause can also reduce disputes over whether later emails or revised drafts changed the original agreement.

Use electronic signatures and eIDAS-compliant solutions

In the EU, electronic signatures remain governed by the eIDAS framework, updated by Regulation (EU) 2024/1183. Electronic signatures cannot be denied legal effect solely because they are electronic, while a qualified electronic signature (QES) has the equivalent legal effect of a handwritten signature across the EU.

Businesses should also preserve signer identification, timestamps, audit trails, and evidence of signing authority.

Confirm key terms and keep records

After negotiations by email, phone, or messenger, confirm the agreed terms in writing. Businesses should also retain drafts, approvals, invoices, payment records, and electronic signature logs in a centralised archive.

Define a clear dispute resolution mechanism

Cross-border contracts should clearly specify governing law, jurisdiction, or arbitration rules to reduce uncertainty if a dispute arises.

How can Key2Law help with unsigned contracts and their enforcement?

Disputes over unsigned contracts often depend on details: how the parties negotiated, whether essential terms were agreed, who had authority to approve them, and what happened after the agreement was reached. Key2Law team advises businesses on contract formation, evidence, enforcement, and dispute prevention across different jurisdictions.

Our team can help you:

• Assess whether an unsigned agreement may be legally enforceable;
• Review emails, messages, invoices, payment records, and other evidence of mutual consent;
• Identify applicable formal requirements and potential weaknesses in the agreement;
• Prepare demand letters and develop an enforcement strategy;
• Review automatic renewal clauses, termination provisions, and other terms that may affect the parties’ continuing obligations;
• Assess sanctions clauses in contracts and other compliance provisions relevant to cross-border agreements;
• Support negotiations, settlement discussions, and further legal proceedings where necessary.

If a counterparty denies the existence of an agreement or refuses to perform because the contract was not formally signed, contact Key2Law. Our lawyers can review the available evidence, assess the applicable law, and help determine the most effective way to protect and enforce your rights.