A sales or purchase agreement is a fundamental contract in the law of obligations. The concept of a sales contract is defined by the OZ as follows:

“A sales contract is an agreement in which the seller undertakes to deliver the sold item to the buyer in such a way that the buyer acquires ownership, while the buyer undertakes to pay the purchase price to the seller. If the subject of the sale is a right, the seller undertakes to provide the buyer with the sold right; if the exercise of this right requires possession of the item, the seller must also deliver the item.”²⁰²

A sales contract is a bilateral, remunerative legal transaction between a seller and a buyer. It is also a reciprocal contract, meaning both parties must perform certain actions, such as giving, doing, or refraining from something. The buyer must pay the purchase price, while the seller must transfer ownership of the item to the buyer.

The essential element of a sales contract is the item being sold, while the price (purchase price) is not always considered an essential component.²⁰³ The purchase price must be expressed in money, as the essence of a sales contract is the transfer of ownership rights in exchange for money. If the obligation opposed to the transfer of rights consists of something other than money, the transaction may constitute an exchange contract or another type of agreement. The determination of the purchase price is primarily a matter of agreement between the contracting parties and is usually specified as a certain amount of monetary units that the buyer must pay.²⁰⁴

The seller’s primary obligation is to transfer ownership of the item. The buyer’s primary obligation is to pay the purchase price, which is expressed in money as a measure of value.

A seller may also sell a right rather than a physical object. In this case, the seller undertakes to provide the buyer with the sold right. If exercising the right requires possession of an item, the seller must also deliver the item related to the right. The subject of sale may also include a claim from an obligation relationship in which the seller has the position of a creditor.²⁰⁵

^{202 See Art. 435 of OZ.}