A Bill Auction, also known as a Treasury bill auction, is a public sale of U.S. Treasury bills by the United States Department of the Treasury. The auctions are held every week and offer debt obligations with maturities ranging from one month to one year. As of May 2021, there are 24 authorized primary dealers who must participate in the auctions and bid directly on each issue.The bill auction is an official way in which all U.S. Treasury bills are issued and it occurs weekly. The auctions offer debt obligations with various maturities (ranging from one month to one year) to interested buyers, including primary dealers who must participate in order to bid on each issue directly.