A certificate of title, also known as an opinion letter, gives an opinion stating that the title is vested in a particular individual. A certificate of sale is issued to a buyer at a judicial sale and entitles a buyer to the deed upon confirmation of sale by court. An estoppel certificate, sometimes called a certificate of no defense, is a legal instrument used by the bank to stop the mortgage and to indicate what the mortgage balance is on a certain date, after which the mortgagor has no defense unless he/she contests in a timely manner.