Definition of Acceptance: In terms of Section 2(b) of the Act, ‘the term acceptance’ is defined as follows:
“When the person to whom the proposal is made signifies his assent thereto, proposal is said to be accepted. The proposal, when accepted, becomes a promise”.
Analysis of the above definition
1. When the person to whom proposal is made - for example if A offers to sell his car to B for Rs. 200000. Here, proposal is made to B.
2. The person to whom proposal is made i.e. B in the above example and if B signifies his assent on that proposal. In other words if B grants his consent on A’s proposal, then we can say that B has signified his consent on the proposal made by A.
3. When B has signified his consent on that proposal, we can say that the proposal has been accepted.
4. Accepted proposal becomes promise.
Relationship between offer and acceptance: According to Sir William Anson “Acceptance is to offer what a lighted match is to a train of gun powder”. The effect of this observation is that what acceptance triggers cannot be recalled or undone. But there is a choice to the person who had the train to remove it before the match is applied. It in effect means that the offer can be withdrawn just before it is accepted. Acceptance converts the offer into a promise and then it is too late to revoke it. This means as soon as the train of gun powder is lighted it would explode. Train of Gun powder [offer] in itself is inert, but it is the lighted match [the acceptance] which causes the gun powder to explode. The significance of this is an offer in itself cannot create any legal relationship but it is the acceptance by the offeree which creates a legal relationship. Once an offer is accepted it becomes a promise and cannot be withdrawn or revoked. An offer remains an offer so long as it is not accepted but becomes a contract as soon as it is accepted.
Legal Rules regarding a valid acceptance
(1) Acceptance can be given only by the person to whom offer is made: In case of a specific offer, it can be accepted only by the person to whom it is made. [Boulton vs. Jones (1857)]
Case Law: Boulton vs. Jones (1857)
Facts: Boulton bought a business from Brocklehurst. Jones, who was Broklehurst’s creditor, placed an order with Brocklehurst for the supply of certain goods. Boulton supplied the goods even though the order was not in his name. Jones refused to pay Boultan for the goods because by entering into the contract with Blocklehurst, he intended to set of his debt against Brocklehurst. Held, as the offer was not made to Boulton, therefore, there was no contract between Boulton and Jones.
In case of a general offer, it can be accepted by any person who has the knowledge of the offer. [Carlill vs. Carbolic Smoke Ball Co. (1893)]
(2) Acceptance must be absolute and unqualified: As per section 7 of the Act, acceptance is valid only when it is absolute and unqualified and is also expressed in some usual and reasonable manner unless the proposal prescribes the manner in which it must be accepted. If the proposal prescribes the manner in which it must be accepted, then it must be accepted accordingly.
Example: ‘A’ enquires from ‘B’, “Will you purchase my car for Rs. 2 lakhs?” If ‘B’ replies “I shall purchase your car for Rs. 2 lakhs, if you buy my motorcycle for Rs. 50000, here ‘B’ cannot be considered to have accepted the proposal. If on the other hand ‘B’ agrees to purchase the car from ‘A’ as per his proposal subject to availability of valid Registration Certificate / book for the car, then the acceptance is in place though the offer contained no mention of R.C. book. This is because expecting a valid title for the car is not a condition. Therefore the acceptance in this case is unconditional.
(3) The acceptance must be communicated: To conclude a contract between the parties, the acceptance must be communicated in some perceptible form. Any conditional acceptance or acceptance with varying or too deviant conditions is no acceptance. Such conditional acceptance is a counter proposal and has to be accepted by the proposer, if the original proposal has to materialize into a contract. Further when a proposal is accepted, the offeree must have the knowledge of the offer made to him. If he does not have the knowledge, there can be no acceptance. The acceptance must relate specifically to the offer made. Then only it can materialize into a contract. The above points will be clearer from the following examples,
(a) Brogden vs. Metropolitan Railway Co. (1877) Facts: B a supplier, sent a draft agreement relating to the supply of coal to the manager of railway Co. viz, Metropolitian railway for his acceptance. The manager wrote the word “Approved” on the same and put the draft agreement in the drawer of the table intending to send it to the company’s solicitors for a formal contract to be drawn up. By an over sight the draft agreement remained in drawer. Held, that there was no contract as the manager had not communicated his acceptance to the supplier, B.
(b) M offered to sell his land to N for £280. N replied purporting to accept the offer but enclosed a cheque for £ 80 only. He promised to pay the balance of £ 200 by monthly installments of £ 50 each. It was held that N could not enforce his acceptance because it was not an unqualified one. [Neale vs. Merret  W. N. 189].
(c) A offers to sell his house to B for Rs. 1,00,000/-. B replied that, “I can pay Rs. 80,000 for it. The offer of ‘A’ is rejected by ‘B’ as the acceptance is not unqualified. B however changes his mind and is prepared to pay Rs. 1,00,000/-. This is also treated as counter offer and it is upto A whether to accept it or not. [Union of India v. Bahulal AIR 1968 Bombay 294].
Where an offer made by the intended offeree without the knowledge that an offer has been made to him cannot be deemed as an acceptance thereto. (Bhagwandas v. Girdharilal) A mere variation in the language not involving any difference in substance would not make the acceptance ineffective. [Heyworth vs. Knight  144 ER 120].
(4) Acceptance must be in the prescribed mode: Where the mode of acceptance is prescribed in the proposal, it must be accepted in that manner. But if the proposer does not insist on the proposal being accepted in the manner prescribed after it has been accepted otherwise, i.e., not in the prescribed manner, the proposer is presumed to have consented to the acceptance.
Example: If the offeror prescribes acceptance through messenger and offeree sends acceptance by email, there is no acceptance of the offer if the offeror informs the offeree that the acceptance is not according to the mode prescribed. But if the offeror fails to do so, it will be presumed that he has accepted the acceptance and a valid contract will arise. (5) Time: Acceptance must be given within the specified time limit, if any, and if no time is stipulated, acceptance must be given within the reasonable time and before the offer lapses. What is reasonable time is nowhere defined in the law and thus would depend on facts and circumstances of the particular case.
(6) Mere silence is not acceptance: The acceptance of an offer cannot be implied from the silence of the offeree or his failure to answer, unless the offeree has in any previous conduct indicated that his silence is the evidence of acceptance.
Case Law: Felthouse vs. Bindley (1862) Facts: F (Uncle) offered to buy his nephew’s horse for £30 saying “If I hear no more about it I shall consider the horse mine at £30.” The nephew did not reply to F at all. He told his auctioneer, B to keep the particular horse out of sale of his farm stock as he intended to reserve it for his uncle. By mistake the auctioneer sold the horse. F sued him for conversion of his property. Held, F could not succeed as his nephew had not communicated the acceptance to him.
Example: ’A’ subscribed for the weekly magazine for one year. Even after expiry of his subscription, the magazine company continued to send him magazine for five years. And also ‘A’ continued to use the magazine but denied to pay the bills sent to him. ’A’ would be liable to pay as his continued use of the magazine was his acceptance of the offer.
(7) Acceptance by conduct/Implied Acceptance: Section 8 of the Act lays down that “the performance of the conditions of a proposal, or the acceptance of any consideration for a reciprocal promise which may be offered with a proposal, constitutes an acceptance of the proposal. This section provides the acceptance of the proposal by conduct as against other modes of acceptance i.e. verbal or written communication. Therefore, when a person performs the act intended by the proposer as the consideration for the promise offered by him, the performance of the act constitutes acceptance.
For example: when a tradesman receives an order from a customer and executes the order by sending the goods, the customer’s order for goods constitutes the offer, which has been accepted by the trades man subsequently by sending the goods. It is a case of acceptance by conduct.