Supreme Court laid the law down with respect to Contracts signed by Vendor alone are valid or not.

From Para 7,

7) We find that neither of the two decisions have addressed the real issue and cannot be said to be laying down the correct law. The observation in Md. Mohar Ali (supra) stating that an agreement of sale is an unilateral contract is not correct. An unilateral contract refers to a gratuitous promise where only party makes a promise without a return promise. Unilateral contract is explained thus by John D. Calamari & Joseph M. Perillo in The Law of Contracts (4th Edition Para 2-10(a) at pages 64-65):

“If A says to B, ‘If you walk across the Brooklyn Bridge I will pay you $ 100,’ A has made a promise but has not asked B for a return promise. A has asked B to perform, not a commitment to perform. A has thus made an offer looking to a unilateral contract. B cannot accept this offer by promising to walk the bridge. B must accept, if at all, by performing the act. Because no return promise is requested, at no point is B bound to perform. If B does perform, a contract involving two parties is created, but the contract is classified as unilateral because only one party is ever under an obligation.”

All agreements of sale are bilateral contracts as promises are made by both – the vendor agreeing to sell and the purchaser agreeing to purchase. On the other hand, the observation in S.M. Gopal Chetty (supra) that unless agreement is signed both by the vendor and purchaser, it is not a valid contract is also not sound. An agreement of sale comes into existence when the vendor agrees to sell and the purchaser agrees to purchase, for an agreed consideration on agreed terms. It can be oral. It can be by exchange of communications which may or may not be signed. It may be by a single document signed by both parties. It can also be by a document in two parts, each party signing one copy and then exchanging the signed copy as a consequence of which the purchaser has the copy signed by the vendor and a vendor has a copy signed by the purchaser. Or it can be by the vendor executing the document and delivering it to the purchaser who accepts it. Section 10 of the Act provides all agreements are contracts if they are made by the free consent by the parties competent to contract, for a lawful consideration and with a lawful object, and are not expressly declared to be void under the provisions of the Contract Act. The proviso to section 10 of the Act makes it clear that the section will not apply to contracts which are required to be made in writing or in the presence of witnesses or any law relating to registration of documents. Our attention has not been drawn to any law applicable in Bihar at the relevant time, which requires an agreement of sale to be made in writing or in the presence of witnesses or to be registered. Therefore, even an oral agreement to sell is valid. If so, a written agreement signed by one of the parties, if it evidences such an oral agreement will also be valid. In any agreement of sale, the terms are always negotiated and thereafter reduced in the form of an agreement of sale and signed by both parties or the vendor alone (unless it is by a series of offers and counter-offers by letters or other modes of recognized communication). In India, an agreement of sale signed by the vendor alone and delivered to the purchaser, and accepted by the purchaser, has always been considered to be a valid contract. In the event of breach by the vendor, it can be specifically enforced by the purchaser. There is, however, no practice of purchaser alone signing an agreement of sale.

An earlier order whereby Aloka Bose (LR of Kanika Bose) was brought on record of case: