The reliance interest is a damage theory in the law of contracts. In short, when there is a breach of contract, one can pursue the reliance interest to get back in damages an amount sufficient to put one in the position that one would have been in had the contract not been signed. For example: Seller contracts with buyer to sell 1000 bushels of apples at 8 dollars a bushel. Buyer buys a machine to turn the apples into applesauce, at a cost of 5000 dollars. Seller breaches. Pursuing reliance interest, the buyer can sue for the cost of the applesauce machine, which buyer purchased in reliance of the delivery of the apples from the seller.