Unilateral Contract, Bilateral Contract, or Quasi Contract?

Distinguish unilateral, bilateral, and quasi contracts by acceptance and remedy, then apply the rules to fact-qualified REG examples.

Quick answer

A bilateral contract exchanges promises. A unilateral contract asks for performance and is accepted by the requested performance. A quasi contract is not an actual agreement; it is a restitutionary obligation imposed by law in qualifying circumstances to prevent unjust enrichment. Governing law and facts can change the result.

Classify by what creates the obligation

Use three questions: what did the offer request, how did the other party respond, and is there an actual agreement? Promise for promise points toward bilateral formation. Promise for completed performance points toward unilateral formation. No agreement plus a qualifying retained benefit points toward quasi-contract restitution.

The 2026 AICPA Blueprint expressly includes unilateral, express, and implied contracts in REG contract formation and validity. It does not separately assign published weighting to bilateral or quasi contract. Section-wide scope remains with the REG hub.

Promise, performance, and restitution compared
CategoryTriggerWhat counts as acceptanceActual contract?Primary exam clue
Bilateral contractOffer requests a return promiseThe offeree gives the requested promiseYes, if formation requirements are metPromise exchanged for promise
Unilateral contractOffer requests performanceThe offeree performs as requestedYes, if formation requirements are metPromise exchanged for performance
Quasi contractOne party receives a benefit under facts supporting restitutionNo contractual acceptance is requiredNoObligation imposed by law to prevent unjust enrichment

Worked comparison: equipment sale, reward, and mistaken benefit

  1. 1Bilateral example: a seller promises to deliver equipment next month, and a buyer promises to pay $24,000 on delivery. The promises are exchanged now. Later performance satisfies those promises; it is not what creates the initial acceptance in this simplified fact pattern.
  2. 2Unilateral example: an owner promises $500 to a person who returns specifically described missing equipment. The offer requests return of the equipment rather than a return promise. If a person with the required knowledge performs as requested while the offer remains effective, the performance can supply acceptance. Do not assume every reward fact pattern reaches that result.
  3. 3Quasi-contract example: a supplier mistakenly delivers a usable benefit to a recipient with whom it has no actual agreement. The recipient recognizes the mistake and retains the benefit. Depending on the governing law and complete facts, restitution may be considered to prevent unjust enrichment. The obligation would be imposed by law, not inferred from mutual assent.
  4. 4The classification sequence is more important than the nouns. Equipment, rewards, employment, and insurance labels do not create universal results. Identify the requested acceptance, conduct, timing, knowledge, benefit, and governing rule supplied by the question.
  5. 5After the comparison, try free REG practice. Apply the classification first, then analyze the remaining formation, defense, performance, or remedy issue stated in the question.
Classify the legal relationship in four questions
  1. 1Is an actual agreement alleged?If not, test whether a fact-qualified restitution theory is presented rather than forcing a contract label.
  2. 2What does the offer request?Identify whether the offer calls for a return promise or completion of a specified performance.
  3. 3How did the offeree respond?Match the response to the requested mode of acceptance instead of relying on the transaction label.
  4. 4What law and facts control?Check formation, enforceability, defenses, and restitution limits in the question before selecting a result.
Three worked classifications and their distractors
ScenarioClassificationReasoningCommon distractor
Seller promises delivery; buyer promises $24,000 paymentBilateralEach party gives the requested promiseCalling it unilateral because delivery occurs later
Owner promises $500 to a finder who returns specified equipmentPotential unilateral formationThe offer requests the stated performance as acceptanceTreating every reward as automatically enforceable
A supplier mistakenly delivers a usable benefit; recipient knowingly retains it without an actual agreementPotential quasi-contract restitutionThe issue is a law-imposed obligation based on qualifying unjust enrichment factsCalling it an implied-in-fact agreement

Practice the CPA topics covered on this page

Practice CPA exam questions and use your results to find the topics that need more work.

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Bilateral and unilateral describe the acceptance bargain

A bilateral offer seeks a commitment. The offeree accepts by making the requested promise, so both parties have outstanding promises to perform. A later failure to perform can create a breach issue, but it does not retroactively change the original promise-for-promise classification.

A unilateral offer seeks the specified performance. A promise to perform later is not necessarily the requested acceptance. Read the offer closely and apply the rules provided for beginning, completing, revoking, or otherwise affecting performance.

Federal opinions used in this guide describe the core promise-versus-performance distinction. They do not create one universal result for every jurisdiction or transaction. On a REG question, use the facts and rules given rather than importing a broad slogan.

Quasi contract is restitution, not implied agreement

1An implied-in-fact contract is still an actual agreement inferred from conduct. Quasi contract is different: it describes a law-imposed obligation even though no actual agreement supplies the basis for recovery.
2A useful sequence is benefit, knowledge or appreciation, retention, inequity, and applicable limitations, but the required elements and available remedy depend on governing law. Do not turn a study sequence into a universal legal test.
3A Fifth Circuit opinion in the research record discusses a Texas-specific limitation involving an express contract. Keep that limitation labeled to its legal context. Do not publish the broader claim that an express contract always bars every restitution theory everywhere.
4The exam distinction is conceptual: mutual assent supports an express or implied-in-fact contract; restitution supplies a possible law-imposed obligation when qualifying facts exist without that actual agreement.

Keep the classification inside the REG scope boundary

This page owns the three literal classification queries and the promise-performance-restitution comparison. It does not replace the Blueprint or take section-wide study-guide, format, or weighting intent from the CPA Exam Blueprints and REG hub.

Suretyship and guaranty, contract performance, discharge, breach, remedies, debtor-creditor relationships, and guarantor rules remain adjacent doctrines. A question may combine them, but classification is only the first step.

The Blueprint names unilateral, express, and implied contracts within its Business Law outline. It does not publish separate weighting for bilateral or quasi contract. Do not invent a scoring priority from the presence or absence of an individual label.

These examples are CPA Exam study explanations, not legal advice. Real disputes require the governing jurisdiction, full record, procedural posture, and qualified legal analysis.

REG owner boundary for contract questions
  1. 1This pageClassify bilateral, unilateral, and quasi-contract fact patterns by promise, performance, agreement, and restitution.
  2. 2REG section hubKeep section-wide format, weighting, study-guide, and Business Law coverage with the REG owner.
  3. 3Adjacent contract doctrinesKeep suretyship, guaranty, performance, discharge, breach, remedies, and debtor-creditor analysis separate.
  4. 4Question facts and governing lawUse the stated rules and facts; this study guide is not legal advice for a real transaction.

Use a repeatable REG question sequence

  • Identify the alleged agreement, offeror, offeree, requested acceptance, response, and timing.
  • If the offer requests a promise, test bilateral formation. If it requests performance, test unilateral formation under the supplied facts and law.
  • If no actual agreement exists, separate implied-in-fact assent from a possible quasi-contract restitution theory.
  • Then analyze consideration, capacity, legality, defenses, writing requirements, performance, discharge, breach, or remedy only as the question requires.
  • Reject distractors that make every reward, insurance, or employment relationship unilateral, equate quasi contract with implied-in-fact contract, or claim universal restitution rules.
  • Use REG practice to rehearse the sequence and keep your error log focused on classification, formation, defense, or remedy rather than memorizing transaction labels.
  • For a mixed-section question set after the REG drill, return to CPA practice questions without transferring this page's narrow contract-type ownership to a general practice route.

Frequently asked questions

What is a unilateral contract?

A unilateral contract is formed when an offer requests acceptance by performance and the requested performance occurs. The exact legal result depends on the offer, facts, governing law, and stage of performance.

What is a bilateral contract?

A bilateral contract exchanges promises. Each party becomes bound by a promise, and the return promise is the requested acceptance rather than completion of the promised performance.

What is a quasi contract?

A quasi contract is not an actual contract. It is a restitutionary obligation imposed by law in qualifying circumstances to prevent unjust enrichment. It should not be confused with an implied-in-fact agreement.

Are all rewards unilateral contracts?

No universal classification should be applied from the label alone. A classic reward offer may request acceptance by completed performance, but wording, knowledge, conduct, governing law, revocation, and other facts can change the analysis.

Sources