Acceptance in contract law is when a person agrees to the terms of an offer without any changes. An offer is a proposal from one party to another intending to create a legal obligation upon acceptance.In contract law it is what the parties say or do that matters; not, what they mean. The traditional contract law rule is that an acceptance must be the mirror image of the offer. Unilateral Contracts. The formation of a valid contract is ultimately dependent on the offeracceptance paradigm, which is a series of backandforth manifestations of intent.