The present invention relates to a system and a method for performing sale actions of a product or service through a communication network (300) which comprises: sending to one seller (100) the specifications of the product or service with a reference price, so that the seller (100) can present one or more offers (10) to be put up for sale; receiving, from the seller (100), the offer (10) for of product or service to be put up for sale; storing the offer (10) in a database (310) of the communication network (300); receiving, from a plurality of buyers (200), a plurality of purchase proposals (20) for the product or service, the plurality of purchase proposals (20) being determined for the offer (10) of the seller (100); storing the plurality of purchase proposals (20) in the database (310) of the communication network (300); processing the plurality of purchase proposals (20) and determining a product or service matrix, the matrix being constituted by the plurality of purchase proposals (20) received for the offer (10); monitoring when the seller (100) takes a new lot (30) at his opportune moment or at the time limit, in the course of the auction, at the price of his interest to sell the product or service to the plurality of buyers (200) who has given the plurality of units corresponding to the purchase proposals (20) of the respective lot (30).