This is also a formal document binding on both parties and signed by them in the presence of a Notary Public. It is used primarily for the purpose of conveying the property from the seller to the buyer.
In case of a cash purchase, it is simpler and cheaper to go directly from verbal negotiations to the signing of the "Contrato de Venta", instead of taking the preliminary step of signing a Promise of Sale or "Promesa de Venta". All funds from the buyer should ready before the closing date.
Both parties need to be physically present in front of the Public Notary, or their legal representant (via Power of Attorney). It will be read and signed by both parties.