There seems to be some interest, so heres a very quick example of what happens when you buy a 4-week $1,000 T-Bill.
1) Open an account at TreasuryDirect, link up checking/savings account.
2) Login, and select your amount and maturity date ($1,000)
3) You must schedule the purchase before Noon EST on the auction date (Tuesdays), otherwise you are pushed to next week.
4) Auction occurs on Tuesday, and on Thursday the discounted amount ($99x.xx) is taken out of your account.
5) 28 days later, also on a Thursday, $1000 is put back into your account if you choose so. If there is a holiday both the purchase and maturity dates are moved together.
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Treasury securities are government bonds issued by the United States Department of the Treasury through the Bureau of the Public Debt. They are the debt financing instruments of the U.S. Federal government, and are often referred to simply as Treasuries or Treasurys. There are four types of treasury securities: Treasury bills, Treasury notes, Treasury bonds, and Savings bonds. All of the Treasury securities (besides savings bonds) are very liquid and are heavily traded on the secondary market.
Treasury bills (or T-bills) mature in one year or less. Like zero-coupon bonds, they do not pay interest prior to maturity; instead they are sold at a discount of the par value to create a positive yield to maturity.