A type of khiyar (Islamic option) which is given to the buyer so that if the seller has glossed over the object of sale, showing features that are not actually part of it, the buyer would have the right either to revoke the contract or to consummate it. This option (in Arabic script: خيار التدليس) comes into effect in cases where sellers conceal unattractive features under a deceptively attractive appearance. Tadlis (fraudulent concealment of defects- uyub, sing. aib or ayb) is prohibited by shari’a.

An example of tadlis is when a farmer keeps his cows unmilked for quite a while in an attempt to delude an unsuspecting buyer into purchasing them for their ability to produce overabundant milk.