Mutual vs. Unilateral Mistake: What Makes an Agreement Voidable?

Q: Quick Answer: What Is the Difference Between Mutual and Unilateral Mistake?

A mutual mistake generally involves both parties entering into an agreement while sharing a mistaken belief about an important fact. A unilateral mistake generally occurs when only one party is mistaken. Mutual mistakes may provide grounds for certain forms of court relief when the mistake is material, while unilateral mistakes are generally more difficult to use as a basis for undoing an agreement unless additional circumstances, such as fraud or inequitable conduct, are involved.

Understanding the Key Differences Between Mutual and Unilateral Mistakes in Illinois Contract Law

When someone signs a settlement or other agreement, the general assumption is that the agreement is final. However, mistakes can happen during contract formation. In certain circumstances, Illinois courts may recognize that an agreement can be challenged, rescinded, or otherwise affected when a material mistake played an important role in the parties entering into the contract.

While Illinois courts recognize that mistakes can occur during contract formation, not all mistakes are treated equally. It is important to understand the critical legal distinction between a mutual mistake and a unilateral mistake, and how that distinction may affect whether a contract can potentially be voided or otherwise modified.

This article provides a general overview of mistakes in contracting and how these concepts may arise in settlement agreements and other legal contracts. For official legal advice specific to your circumstances, contact an experienced attorney at Patel Law, PC.

Quick Answer: What Is the Difference Between Mutual and Unilateral Mistake?

A mutual mistake generally involves both parties entering into an agreement while sharing a mistaken belief about an important fact. A unilateral mistake generally occurs when only one party is mistaken. Mutual mistakes may provide grounds for certain forms of court relief when the mistake is material, while unilateral mistakes are generally more difficult to use as a basis for undoing an agreement unless additional circumstances, such as fraud or inequitable conduct, are involved.

What Is a Mutual Mistake?

A mutual mistake may be present when both parties to a contract are mistaken about a material fact connected to the agreement. The mistaken belief generally must concern an important fact that goes to the heart of the agreement rather than a minor or unrelated detail.

In certain circumstances, a court may consider whether the agreement should be rescinded or reformed because both parties entered into it based on the same mistaken understanding.

The Key Question

In a mutual mistake situation, an important question is whether both parties shared the same mistaken belief about a material fact when they entered into the agreement.

What Is a Unilateral Mistake?

A unilateral mistake occurs when only one party to an agreement is mistaken regarding a material fact while the other party understands the relevant circumstances differently.

Courts generally do not automatically rescind contracts simply because one party later realizes that they misunderstood an important fact. However, exceptions may exist when additional circumstances are present, including allegations involving fraud, misrepresentation, or inequitable conduct.

Why the Difference Matters

Whether a mistake was shared by both parties or made by only one party can significantly affect how a court evaluates a request to rescind, reform, or otherwise challenge an agreement.

Mutual Mistake vs. Unilateral Mistake

The following comparison provides a general visual overview of the differences between these two concepts.

Issue	Mutual Mistake	Unilateral Mistake
Who is mistaken?	Both parties share a mistaken belief about an important fact.	Only one party is mistaken.
Does the mistake need to matter?	Generally, the mistake must involve a material fact connected to the agreement.	The significance of the mistake and surrounding circumstances may affect whether relief is available.
Is court relief possible?	Potentially, depending on whether the shared mistake was material to the agreement.	Generally more difficult, although fraud, misrepresentation, or inequitable conduct may affect the analysis.

Sample Scenario: How a Mutual Mistake May Arise

The following simplified example illustrates how a mutual mistake may potentially arise in the context of a settlement or release agreement.

Chemical Exposure Occurs

An employee working at a chemical storage facility is exposed to a chemical after a containment issue results in the substance being released inside the facility.

A Medical Condition Is Evaluated

Following the exposure, the employee develops an unusual mole and seeks medical attention. A sample is sent to a laboratory, and the employee is initially informed that the mole is benign and does not present a medical concern.

A Release Agreement Is Signed

The employee informs the employer of the diagnosis and signs a release relating to the chemical exposure and the mole based on the understanding that the medical condition is benign.

The Original Test Results Are Questioned

Two weeks later, the dermatologist contacts the employee and explains that there may have been a mix-up involving the laboratory samples and that the original test results may have been reported incorrectly.

A New Diagnosis Is Received

The mole is tested again and the new results indicate that the mole is cancerous. The circumstances surrounding the release and the parties’ understanding of the medical condition would then need to be carefully evaluated.

How the Mutual Mistake Issue Could Be Evaluated

The sample scenario above would require several legal and factual issues to be properly evaluated. However, at a basic level, the example illustrates why a shared misunderstanding about an important fact may become legally significant.

The employee and employer entered into the release based on the understanding that the mole was benign. If that understanding resulted from incorrect laboratory information, the parties may have entered into the agreement while sharing the same mistaken belief about a fact closely connected to the purpose of the release.

Whether an agreement could actually be rescinded, reformed, or otherwise challenged would depend on the specific facts, the language of the agreement, applicable Illinois law, and other circumstances surrounding the situation.

Why the Facts Matter

Contract disputes involving mistake can depend heavily on the precise facts of the situation. The language of the agreement, the information available to each party, the timing of events, and whether the mistaken fact was material can all affect the legal analysis.

Why Legal Guidance Can Be Important Before Signing an Agreement

Settlement agreements and releases can have significant legal consequences. Before signing an agreement, it may be important to understand exactly what claims are being released and what information the agreement is based upon.

Once an agreement is signed, attempting to challenge or undo it may involve complicated legal issues. An attorney can help review the circumstances surrounding an agreement and explain potential options based on the specific facts of the situation.

Agreements Should Be Reviewed Carefully

A settlement or release may affect important legal rights. Before signing, it can be beneficial to understand the scope of the agreement and discuss any questions or concerns with experienced legal counsel.

Contact Patel Law, PC

Contract disputes and settlement issues can introduce unexpected complications into a personal injury lawsuit. Understanding the difference between a mutual mistake and a unilateral mistake may be an important part of evaluating whether an agreement should be reviewed more closely.

A Danville personal injury attorney at Patel Law, PC can help you navigate unexpected developments and legal issues that may arise during your personal injury case. Contact our office today to begin speaking with our dedicated team.

Frequently Asked Questions About Mistakes in Contracts

What is a mutual mistake in a contract?

A mutual mistake generally occurs when both parties enter into an agreement while sharing the same mistaken belief about a material fact connected to the agreement.

What is a unilateral mistake?

A unilateral mistake generally occurs when only one party is mistaken about a material fact while the other party does not share that same mistaken belief.

Can a contract be voided because of a mistake?

The answer depends on the specific facts and applicable law. Courts may consider whether the mistake was material, whether both parties shared the mistaken belief, and whether other circumstances such as fraud or misrepresentation are present.

Is it difficult to undo a settlement agreement?

Settlement agreements can involve significant legal rights and obligations. Challenging an agreement after it has been signed may involve complex legal and factual issues, making it important to seek legal advice regarding the specific circumstances involved.

Should I speak with an attorney before signing a release?

Speaking with an experienced attorney may help you understand the legal rights you may be giving up and the potential consequences of signing a settlement or release agreement.

Questions About a Settlement or Release Agreement?

A mistake involving an important fact can sometimes raise serious questions about an agreement and the legal rights affected by that agreement.

The legal team at Patel Law, PC can help you better understand the circumstances surrounding your personal injury matter and discuss potential legal options available in your situation.