Section 5 of the Indian Contract says A proposal may be revoked at any time before the communication of its acceptance is complete as against the proposer, but not afterwards. An acceptance may be revoked at any time before the communication of the acceptance is complete as against the acceptor, but not afterwards. An emphasis on the word communication of acceptance is to be made.
Communication of acceptance according to Section 4 of the Indian Contract Act,1872 is said to be completed when the said communication comes to the knowledge of the person who made the offer. The communication of acceptance can be understood in two multiple aspects.
In the given question of law to be discussed the acceptance would be considered valid and revocation will be declared ineffective as the acceptance of proposal will be completed as soon as the letter is put in transmission i.e it become out of the power of the acceptor to make any change, and revocation of the acceptance will only be completed as soon as the offeror is made aware of the such revocation. Thus the communication of revocation should reach the offeree before the acceptance is out of his power. In an illustration in section 5 A proposes, by a letter sent by post, to sell his house to B. B accepts the proposal by a letter sent by post. A may revoke his proposal at any time before or at the moment when B posts his letter of acceptance, but not afterwards. B may revoke his acceptance at any time before or at the moment when the letter communicating it reaches A, but not afterwards.
against proposer = Put in transmission, becoming out of his power
against acceptor = when it comes to knowledge of the proposer
Applying the above-mentioned sections and illustration of the bare act, even if the acceptance and revocation were posted by the receiver on different days and reaches the offeror on the same day as the acceptance is completed as soon as it becomes out of his power to make any change, so for revocation of acceptance to be considered effectual, it should be made to the knowledge of the offeror before the letter of acceptance is posted.