This work presents a mathematical model to aid a price-taker seller who offers in a bilateral electricity contract auction. The buyers' demand for electricity is disputed by multiple sellers in a descending, sealed-bid auction, with multiple products, uniform price for each product, and multiple rounds. The model efficiently allocates the seller's offers into the auctioned products, maximizing his financial benefit. It was developed for auctions with the same rules of the Brazilian purchase Auction, a sequence of eleven-monthly auctions that happened from July-03 to June-04. (c) 2008 Elsevier Ltd. All rights reserved.308491495