close a/the sale
To reach an agreement with a buyer; to finalize a sale by persuading the interested party to complete the purchase. We need to move in a month, so how quickly can you close a sale? Obviously, we're looking for salespeople who can consistently close the sale.
close a sale
and close the saleto complete the sale of something; to seal a bargain in the sale of something. The salesman closed the sale and the customer drove off in a brand new car.