MBE Rules · Contracts
Acceptance by performance vs. promise
The rule
A unilateral contract is accepted only by complete performance (beginning to perform creates an option but does not accept). A bilateral contract is accepted by a return promise. If the offer is ambiguous, the offeree may accept either way under UCC §2-206 and Restatement §32.
In plain English
In a unilateral contract, you accept by doing the task. In a bilateral contract, you accept by promising to do the task. If it's unclear, you can accept by either doing the task or promising to do it.
Worked example
The defendant offers $100 to anyone who mows his lawn. Alex mows the lawn, accepting by performance. If the defendant says, 'I'll pay you to mow next week,' Alex accepts by saying, 'I promise to mow then.'
Memory hook
Perform or Promise? Know your path! Unilateral needs full act; bilateral just a nod.
The trap
Students think: Starting a task accepts unilateral contracts. Wrong, because it only creates an option. Full performance is needed.
How examiners test it
Test setup: ambiguous offer for a service. Trap: students assume any start accepts. Look for full performance or a clear promise to determine acceptance.
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