to property is under an equitable duty to convey it to another on the ground that he would be unjustly enriched if he were permitted to retain it. Basis of the law should be restitution where it is unreasonable and unjust for the defendant to retain the benefit which he has received. The theory of implied contract still persists in law. “Restitution” means the restoring of anything unlawfully taken from another. It is most frequently used in the common law for setting them in possession of land and tenements that has been unlawfully dispossessed of them. Looked at from another angle under Section 72 of the Indian Contract Act, a person to whom money has been paid, or anything delivered, by mistake or under coercion, must repay or return it. Section 72 of the Contract Act includes payment made under a bona fide mistake of law. In our view, in case of payment of a tax which is ultra vires or unconstitutional or paid under a mistaken belief or wrong interpretation of the provisions of law, the party is entitled to have a refund or adjustment of it from the State whether he had paid it under protest or not. This also has been the consistent view of the Supreme Court. See [1958] 9 STC 747; AIR 1959 SC 135 (Sales Tax Officer v. Kanhaiya Lal) and [1961] 12 STC 357; AIR 1961 SC 1438 (Orient Paper Mills v. State of Orissa ). While dealing with cases of refund of tax collected without authority of law, the Supreme Court held that where public bodies under colour of public laws recover people’s money, later discovered to be erroneous levies, the dharma of the situation admits of no equivocation. There is no law of limitation especially for public bodies on the virtue of returning what was wrongly recovered to whom it belongs. In our view, what is appropriate in the case of tax collected under an invalid law is applicable to the case of tax paid under a bona fide mistaken belief. The adjustment of the amount in such cases would be in consonance with justice and, equity and good conscience.”