The fact that a revocation becomes effective only when the offeree receives it becomes problematic when offers, acceptances and revocations are sent back and forth through the mail. For example:
On January 1st, Marsha makes a written offer to Jan to sell her a case of Girl Scout cookies for $50. On January 3rd, Marsha writes Jan another letter revoking the offer. Jan receives the offer in the mail on January 6th and immediately writes Marsha a letter accepting the offer. Jan puts her letter of acceptance in the mail on the same day, January 6th. On January 9th, Jan receives Marsha’s letter of revocation. In this situation, Marsha and Jan have a binding contract. As we said earlier, acceptance of an offer is effective upon dispatch. In other words, Jan’s acceptance of Marsha’s offer becomes effective as soon as she puts her letter of acceptance in the mail. However, a revocation of an offer does not become effective until the offeree receives it. Therefore, Jan’s acceptance was valid on January 6th while Marsha’s revocation only became valid on January 9th. That being the case, the offer was still available to Jan on January 6th, even though Marsha wrote her letter of revocation on January 3rd. By the time Jan received Marsha’s letter of revocation, she had already accepted the offer. Therefore, Jan and Marsha have a valid contract and Marsha must sell Jan the cookies for $50.