Jurisprudence, Interpretation and General Laws · Contract Law

Nature and Essentials of a Valid Contract under Indian Contract Act

Updated 11 October 2026 · Fact-checked

A contract is an agreement enforceable by law (Section 2(h)). An agreement is a promise or set of promises forming consideration for each other (Section 2(e)). To solve a question, check proposal, acceptance, consideration, capacity, free consent and lawful object, then classify the result as valid, void, voidable, illegal or unenforceable.

Understand Nature and Essentials of a Valid Contract

Start with the chain of definitions in Section 2 of the Indian Contract Act, 1872. A proposal is when one person signifies willingness to do or abstain from doing something, to obtain the assent of another (Section 2(a)). When the other person signifies assent, the proposal is accepted and becomes a promise (Section 2(b)). The proposer is the promisor; the acceptor is the promisee (Section 2(c)).

Every promise, and every set of promises forming the consideration for each other, is an agreement (Section 2(e)). An agreement enforceable by law is a contract (Section 2(h)). So every contract is an agreement, but not every agreement is a contract. A promise to meet a friend for dinner is an agreement in the everyday sense, but the law does not enforce it as a contract.

The Act does not list all essentials in one place. You build them from the definitions and later sections: a proposal and its acceptance, consideration (Section 2(d)), parties with capacity, free consent, a lawful object and consideration, and agreements not expressly declared void. The topic pages on capacity, consideration, free consent and legality cover each in depth. Here you need the overview and the classification.

Classification depends on enforceability. A valid contract is enforceable by law. A void agreement is not enforceable by law (Section 2(g)). A voidable contract is enforceable at the option of one or more parties but not at the option of the other or others (Section 2(i)). A contract that was valid can later become void when it ceases to be enforceable (Section 2(j)), for example by impossibility under Section 56.

Two more labels appear in exam answers. An illegal agreement is one forbidden by law. It is void, and it also carries penal or other consequences, so contracts collateral to it are also tainted. An unenforceable contract is a contract that is good in substance but cannot be enforced in court because of a technical defect, such as a missing formality or a bar of limitation. The Act itself does not define these two terms, so state them as accepted classifications and do not cite a section.

Key rules to remember

Proposal: Willingness to do or abstain, signified to another, with a view to obtaining that other's assent (Section 2(a)); Intention to obtain assent is what separates a proposal from a mere statement.
Promise: Proposal + acceptance = promise (Section 2(b)); Acceptance means the person to whom the proposal is made signifies assent.
Agreement: Agreement = every promise and every set of promises forming consideration for each other (Section 2(e)); Reciprocal promises are those forming the consideration or part of it for each other (Section 2(f)).
Contract: Contract = agreement enforceable by law (Section 2(h)); Agreement is the wider term; contract is the narrower one.
Void agreement: Agreement not enforceable by law (Section 2(g)); It is void from the start, with no legal effect as a contract.
Voidable contract: Enforceable at the option of one or more parties, not of the other or others (Section 2(i)); The aggrieved party chooses to affirm or avoid. Until avoided, it stands.
Contract becoming void: A contract that ceases to be enforceable becomes void when it ceases to be enforceable (Section 2(j)); Valid at the start, void later. Section 56 supplies an example.
Revocation of proposal: Proposal may be revoked any time before communication of acceptance is complete as against the proposer, not afterwards (Section 5); For a postal acceptance, the proposer can revoke up to the moment the acceptor posts the letter.
Revocation of acceptance: Acceptance may be revoked any time before communication of acceptance is complete as against the acceptor, not afterwards (Section 5); In the Act's postal illustration, the acceptor may revoke until the letter reaches the proposer.
Modes of revoking a proposal: Notice of revocation; lapse of time; failure of a condition precedent; death or insanity of proposer known to acceptor before acceptance (Section 6); Learn all four. Death or insanity works only if the acceptor learns of it before accepting.
Effect of benefit under a void agreement: Person who received an advantage under a void agreement or a contract that becomes void must restore it or compensate for it (Section 65); Useful when a question asks what happens to money already paid.

How to solve Nature and Essentials of a Valid Contract questions

Use this method for any question on the nature of a contract or on classifying an arrangement.

1Define the terms the question tests: proposal, acceptance, promise, agreement and contract, with Section 2 clauses.
2Identify the facts: who proposed, who accepted, when, and how each was communicated.
3Check each essential in turn: proposal and acceptance, consideration, capacity, free consent, lawful object, and no express declaration of voidness.
4Where timing matters, apply Section 5 and Section 6 to see whether the proposal or acceptance was validly revoked or had lapsed.
5Classify the result as valid, void, voidable, illegal or unenforceable, and give the reason in one line.
6State consequences: a voidable contract can be avoided by the aggrieved party; benefits under a void agreement must be restored under Section 65.
7End with a clear conclusion that answers the exact question asked.

Quickest way: Four-line classification check

When to use it: Use it for short-note or case-based questions where time is tight and the facts are brief.

Line 1: Is there a proposal and an acceptance? If no, there is no agreement.
Line 2: Is the agreement enforceable by law? If no, it is void under Section 2(g).
Line 3: If it is enforceable, is it enforceable at the option of only one party? If yes, it is voidable under Section 2(i).
Line 4: Otherwise it is a valid contract. Note any later event that makes it void under Section 2(j) or Section 56.

Common mistakes in Nature and Essentials of a Valid Contract

Treating agreement and contract as the same thing.
Both words are used loosely in daily speech.
Fix: Write both definitions: Section 2(e) for agreement and Section 2(h) for contract. Say every contract is an agreement, but not every agreement is a contract.
Saying a voidable contract is void.
The two words sound alike and both involve a defect.
Fix: A void agreement is not enforceable by law at all. A voidable contract is enforceable until the aggrieved party avoids it. Link voidable to Section 2(i).
Saying a proposal can be revoked until the acceptance reaches the proposer.
Students mix up the rule for the proposer with the rule for the acceptor.
Fix: As against the proposer, acceptance is complete when it is put in the course of transmission. The proposer can revoke only before or at that moment. The acceptor can revoke until the letter reaches the proposer, as the Act's illustration shows.
Forgetting that a contract can become void later.
Students think the class of a contract is fixed at formation.
Fix: Quote Section 2(j) and Section 56. A contract valid when made becomes void when the act becomes impossible or unlawful through an event the promisor could not prevent.
Listing essentials with no reference to the Act.
Students learn the list from memory without linking it to provisions.
Fix: Tie each essential to its source: Section 2(a) and (b) for proposal and acceptance, Section 2(d) for consideration, Section 25 for agreements without consideration, and so on.
Ignoring Section 65 when money has already been paid.
Students stop at the label 'void' and skip the consequence.
Fix: After classifying, add that anyone who received an advantage under a void agreement, or a contract that becomes void, must restore it or compensate for it.

Worked examples

Example 1

A offers by post on 1 March to sell his flat in Pune to B for ₹60,00,000. B posts a letter of acceptance on 3 March. On 3 March, after B has posted the letter, A sends a telegram revoking the offer, which reaches B on 4 March, before B's letter reaches A. Is there a contract? Can B revoke his acceptance?

Show the solution

Provision: Under Section 5, a proposal may be revoked at any time before the communication of its acceptance is complete as against the proposer, but not afterwards.
Under the Act's own illustration, A may revoke his proposal at any time before or at the moment when B posts his letter of acceptance, but not afterwards.
Facts: B had already posted his acceptance on 3 March. So acceptance was complete as against A before A's telegram was sent.
Therefore A's revocation is too late and has no effect on the proposal. A promise has arisen under Section 2(b).
On B's position: Section 5 also says B may revoke his acceptance at any time before the communication of acceptance is complete as against B. The illustration says this is until the letter reaches A.
As B's letter has not yet reached A, B could still revoke his acceptance by a faster communication reaching A before or at the same moment as the letter.

Answer: A's revocation is ineffective because B's acceptance was complete as against A when B posted it. A binding agreement arises, which is a contract if the other essentials are met. B may still revoke his acceptance until his letter reaches A.

Example 2

X agrees to sell a machine to Y for ₹5,00,000. Y pays ₹1,00,000 in advance. Before delivery, a law is passed banning the sale of that type of machine, through no fault of X. Classify the contract and state the position of the advance.

Show the solution

Provision: A contract to do an act which, after the contract is made, becomes unlawful by reason of some event the promisor could not prevent, becomes void when the act becomes unlawful (Section 56, second paragraph).
This also matches Section 2(j): a contract that ceases to be enforceable becomes void when it ceases to be enforceable.
Facts: The contract was valid when made. The ban came afterwards and X could not prevent it.
Classification: The contract was a valid contract at formation. It became void on the date the ban took effect.
Consequence: Under Section 65, a person who has received an advantage under a contract that becomes void must restore it or make compensation for it.
X received ₹1,00,000. X must restore it to Y.

Answer: The contract was valid when made and became void when the sale became unlawful (Sections 2(j) and 56). X must refund the ₹1,00,000 advance to Y under Section 65.

Exam tips

Begin every answer with the definition from Section 2 that the question depends on. Examiners look for the clause number.
For void versus voidable, write one line for each with its clause: Section 2(g) and Section 2(i). Then give a short example of each.
In case-based questions, set out the timeline of proposal, acceptance and revocation before you apply Section 5 and Section 6.
End each answer with a one-line conclusion that names the class of contract and its effect.
When you mention illegal or unenforceable agreements, say they are accepted classifications and do not attach a section number.

Practice questions from Contract Law

Nature and Essentials of a Valid Contract in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Nature and Essentials of a Valid Contract: frequently asked questions

What are the essentials of a valid contract under the Indian Contract Act, 1872?

You need a proposal and its acceptance, consideration, parties with capacity, free consent and a lawful object and consideration. The agreement must not be one that the Act declares void. Together these make an agreement enforceable by law, which is a contract under Section 2(h).

What is the difference between a void and a voidable contract?

A void agreement is not enforceable by law (Section 2(g)). A voidable contract is enforceable at the option of one or more parties but not the other or others (Section 2(i)). The aggrieved party can choose to affirm or reject a voidable contract; nobody can enforce a void one.

Can a valid contract later become void?

Yes. Section 2(j) says a contract that ceases to be enforceable becomes void at that time. Section 56 gives an example: a contract becomes void when the act becomes impossible or unlawful through an event the promisor could not prevent.

When can a proposal be revoked?

A proposal can be revoked any time before the communication of its acceptance is complete as against the proposer (Section 5). Section 6 lists the ways: notice of revocation, lapse of time, failure of a condition precedent, or the proposer's death or insanity if the acceptor knows of it before accepting.