Mistake of Fact vs Mistake of Law under the Indian Contract Act, 1872: Section 21, Mistake as to a Private Right, Foreign Law, and the Recovery of Money Paid under a Mistake of Law

Section 21 states the distinction in a single sentence: a mistake as to a law in force in India does not make a contract voidable, while a mistake as to a law not in force in India has the same effect as a mistake of fact. The rule looks simple and is not. Three qualifications have grown up around it and each is of real practical importance. A mistake as to a private right arising under the general law is treated as a mistake of fact. A foreign law is proved as a fact in Indian courts and is therefore outside the rule. And a mistake of law that leaves the contract perfectly valid may still permit the recovery of money paid under it through Section 72, a route opened by the Supreme Court in 1959 and narrowed by a nine-judge bench in 1997.

Three kinds of mistake about the law, and the separate question of recovering money

1. The Provision and Its Basis

Sections 20, 21 and 72, Indian Contract Act, 1872

20. Where both the parties to an agreement are under a mistake as to a matter of fact essential to the agreement, the agreement is void.

21. Effect of mistakes as to law. A contract is not voidable because it was caused by a mistake as to any law in force in India; but a mistake as to a law not in force in India has the same effect as a mistake of fact.

Illustration. A and B make a contract grounded on the erroneous belief that a particular debt is barred by the Indian law of limitation. The contract is not voidable.

72. A person to whom money has been paid, or anything delivered, by mistake or under coercion, must repay or return it.

The rule in the first limb of Section 21 rests on the maxim ignorantia juris non excusat, ignorance of the law is no excuse. Two reasons are given for it. The practical reason is that every person is presumed to know the law of the land, and a contrary rule would open every transaction to reopening on a plea that is almost impossible to disprove. The institutional reason is that the law must be capable of being ascertained, and a party who has failed to ascertain it cannot be in a better position than one who has taken the trouble.

2. The Distinction in Operation

Kind of mistake	Provision	Effect on the contract
Bilateral mistake of fact, essential to the agreement	Section 20	Void. Advantage received must be restored under Section 65
Unilateral mistake of fact	Section 22	No effect, unless caused by the other party, known to him, or going to identity or to the character of a document
Mistake as to a law in force in India	Section 21, first limb	None. The contract is neither void nor voidable
Mistake as to a law not in force in India	Section 21, second limb	Treated as a mistake of fact, so Section 20 or Section 22 applies according to whether it was bilateral or unilateral
Mistake as to a private right arising under the general law	Section 20, on the authorities	Treated as a mistake of fact, so a bilateral mistake of this kind makes the agreement void

3. Mistake as to a Private Right

The most important qualification is that a mistake about the existence or extent of a private right is treated as a mistake of fact even though the right arises under the general law. The distinction is between the general law, which everyone is presumed to know, and the application of that law to a particular set of facts so as to produce a particular right in a particular person, which nobody can be presumed to know without investigating the facts.

📖 Cooper v. Phibbs, (1867) LR 2 HL 149

Facts: A nephew agreed to take a lease of a salmon fishery from his aunt, both parties believing that the fishery belonged to her. In fact, on the true construction of the settlement under which the family property devolved, the nephew was already the beneficial owner of the fishery, so that he had agreed to take a lease of what was already his own.

Held: The House of Lords set the agreement aside. The parties had contracted under a common mistake as to their respective rights in the property. A mistake as to a private right is not a mistake of the general law within the maxim that ignorance of the law is no excuse; it is a mistake as to a matter of fact, because the existence of the right depends on the particular circumstances of the particular case.

Ratio: A mistake as to the existence or ownership of a private right is treated as a mistake of fact. Where both parties share it and it goes to the root of the agreement, the agreement is liable to be set aside.

The Indian application is straightforward. An agreement by which a person buys property that already belongs to him, both parties believing otherwise, is void under Section 20 as resting on a bilateral mistake as to a matter of fact essential to the agreement. A mistake about whether a statute requires registration, or about the period of limitation applicable to a class of suits, is a mistake as to the general law and falls within Section 21.

4. Mistake as to Foreign Law

The second limb of Section 21 treats a mistake as to a law not in force in India as a mistake of fact. The reason is evidentiary rather than conceptual. In an Indian court a foreign law is not judicially noticed but must be pleaded and proved as a question of fact, ordinarily by expert evidence. It would be incoherent to require a party to prove a foreign law as a fact and then to presume that he knew it.

Three points follow. A bilateral mistake as to a foreign law essential to the agreement makes the agreement void under Section 20. A unilateral mistake as to a foreign law is governed by Section 22 and ordinarily changes nothing. And the law of a foreign State remains foreign for this purpose even where the transaction is otherwise wholly Indian.

5. Money Paid under a Mistake of Law

Section 21 answers a question about the validity of the contract. It says nothing about whether money paid under a mistaken view of the law can be recovered, and that question is governed by Section 72, which sits in Chapter V among the quasi-contractual obligations. The two provisions are frequently confused, and they operate on different subject matter.

📖 Sales Tax Officer, Banaras v. Kanhaiya Lal Mukundlal Saraf, AIR 1959 SC 135

Facts: A firm paid sales tax on its forward transactions in silver bullion under the United Provinces Sales Tax Act. The relevant provision was afterwards held ultra vires by the Allahabad High Court, so the tax had never been payable. The firm sought refund of the amounts paid, and the State resisted on the ground that the payments had been made under a mistake of law and were therefore irrecoverable.

Held: The Supreme Court held the money recoverable. The word mistake in Section 72 is used without qualification and is wide enough to comprehend a mistake of law as well as a mistake of fact. There is nothing in the language of the section to confine it to mistakes of fact, and the English rule denying recovery for mistake of law is not to be imported into a statutory provision expressed in general terms. The State was bound to repay what it had received without authority of law.

Ratio: Section 72 covers money paid under a mistake of law as well as under a mistake of fact. A mistaken view of the law leaves the contract valid under Section 21, but does not prevent recovery of what was paid under that mistake.

⚠ Kanhaiya Lal has been substantially qualified for tax refunds

The proposition that money paid under a mistake of law is recoverable under Section 72 remains good as a matter of general contract law. Its application to claims for refund of indirect taxes was reconsidered by a nine-judge bench in Mafatlal Industries Ltd. v. Union of India, (1997) 5 SCC 536, which held that such claims must ordinarily be pursued under the machinery of the taxing statute and its limitation provisions, and that a refund will be refused where the claimant has passed on the burden of the tax to his customers, since to order repayment would enrich him unjustly at the public expense. The doctrine of unjust enrichment therefore operates as a defence to the claim. This is a specialised field and the position should be verified against the current revenue legislation before it is relied on.

5.1 Defences to a claim under Section 72

Payment in settlement of a disputed claim. Money paid to close a genuine dispute is paid under a compromise and not under a mistake, and cannot be recovered when the paying party afterwards concludes that he was right.
Payment with full knowledge of the facts and of the doubt. A party who pays knowing that the liability is contestable, and choosing to pay rather than litigate, has not paid by mistake.
Change of position. Where the recipient has altered his position irretrievably on the faith of the payment, restitution may be refused.
Unjust enrichment of the claimant, which is the principle applied in Mafatlal to a claimant who has passed the burden on.
Limitation. A suit for money paid under a mistake is governed by Article 113 of the Limitation Act, 1963, and by Section 17, under which time runs from the discovery of the mistake or from when it could with reasonable diligence have been discovered.

6. Why the Distinction Is Criticised

The presumption that everyone knows the law is a fiction. In a system with a very large body of statutory and case law, no one knows the law in any real sense, and the rule denies relief on a premise that is plainly untrue.
The line between fact and law is unstable. The private-right exception concedes as much, since the existence of a right is a conclusion of law drawn from facts, and yet it is treated as a fact.
Section 72 has already displaced the rule for payments, so a party who paid money under a mistake of law may recover it while a party who assumed an obligation under the same mistake cannot escape it.
Other common law jurisdictions have abandoned the bar on recovery for mistake of law, and the Indian position under Section 72 is consistent with that development while Section 21 is not.

7. The Position Stated Shortly

Section 21 makes a mistake as to a law in force in India irrelevant to the validity of a contract, on the maxim that ignorance of the law is no excuse.
A mistake as to a law not in force in India has the same effect as a mistake of fact, because foreign law is proved as a fact.
A mistake as to a private right arising under the general law is treated as a mistake of fact, per Cooper v. Phibbs.
An agreement to buy what already belongs to the buyer, both parties being mistaken, is void under Section 20 on this footing.
Section 21 governs the validity of the contract; Section 72 governs the recovery of money paid.
Kanhaiya Lal: the word mistake in Section 72 covers a mistake of law as well as of fact.
Mafatlal Industries has qualified that position for indirect tax refunds by applying the statutory machinery and the passing-on defence.
Defences to a Section 72 claim include payment in settlement of a dispute, payment with knowledge, change of position, unjust enrichment of the claimant, and limitation.

8. Related Topics and Provisions

Topic or provision	Connection
Mistake under Sections 20 to 22	The full treatment of mistake, including identity and non est factum
Free Consent under Sections 13 and 14	Where mistake sits among the vitiating factors
Types of Contracts	Quasi-contract, of which Section 72 is an instance
Void vs Voidable Contract	Why a bilateral mistake of fact produces voidness
Section 20, Indian Contract Act	Bilateral mistake of fact essential to the agreement
Section 21, Indian Contract Act	Mistake of Indian law and of foreign law
Section 22, Indian Contract Act	Unilateral mistake of fact
Section 65, Indian Contract Act	Restoration where an agreement is discovered to be void
Section 72, Indian Contract Act	Money paid by mistake or under coercion
Sections 17 and 113, Limitation Act, 1963	Limitation for a suit founded on mistake