How Treasury Bills Work

All Treasury bills are short-term investments and mature within a year from their date of issue. You have the option of buying bills with maturity periods of 4 weeks, 8 weeks, 13 weeks, 17 weeks, 26 weeks (6 months), and 52 weeks (1 year) [source: TreasuryDirect]. Generally, the longer the maturity period, the more money you will make from your investment.

The face value of a Treasury bill is called its "par value," and the most commonly sold bills have a par value between $1,000 and $10,000. The minimum amount you can buy a bill for, though, is $100. T-bills are sold in increments of $100 up to $10 million [source: TreasuryDirect].

The purpose of Treasury bills is to help finance the national debt. They are a way for the government to make money from the public. Individuals, people and corporations and foreign governments can buy Treasury bills.

There are many reasons why Treasury bills are popular. Not only are they affordable enough that almost anyone can buy one, but they offer fast returns, and they are simple, easy to understand and very reliable. Additionally, the money you gain from investing in Treasury bills is exempt from state and local taxes. You do have to pay federal income tax on it, however.

Treasury bills are also a highly liquid form of investment. This means that they are easily tradable. They can be sold on the secondary market and easily converted into cash. If you sell a bill on the secondary market, you sell it to someone else instead of waiting for it to mature.

One of the only downsides to Treasury bills is that the returns are smaller than those from many other forms of investment. That's because they are so low risk.

You can purchase Treasury bills at a bank, through a dealer or broker, or online from a website like TreasuryDirect. The bills are issued through an auction bidding process, which occurs weekly. Treasury bills are now issued exclusively in electronic form, though there used to be paper bills.

Before you buy a bill, you have to decide whether to make a competitive or noncompetitive bid. Noncompetitive bidding is the simplest way to purchase a Treasury bill and is what most people do who are not experts in security trading. When you make a noncompetitive bid, you agree to accept whatever interest rate is decided at the auction. You are guaranteed that your bid will be accepted and that you will get the full amount of your bill paid back to you. But you won't know exactly what interest rate you will receive until the auction closes.

In competitive bidding, on the other hand, you specify the return you want to receive. This kind of bidding is usually done by corporations and people who really understand the supply and demand of the securities market. It is more complicated because you don't know whether your bid will be accepted.

If the rate of interest you specify is less than or equal to the rate set by the auction, your bid will be accepted, and you'll receive the uniform rate. This rate is called the "highest accepted yield," and is what all accepted bidders receive, even if they bid for less. For example, if all bids with discount rates between 1.15 percent and 1.25 percent are accepted, you will receive 1.25 percent even if you bid lower. If your bid is higher than the rate set by the auction, however, it will be rejected.

It is through the process of competitive bidding that the discount rates for an auction are decided. A set discount rate is the average from all the competitive bids. It is also the rate that the noncompetitive bidder receives.

For most T-bills, the Treasury holds auctions every week. The exception is the 52-week Treasury bill, which is only auctioned once a month (consult this schedule for more details). For noncompetitive bids, the easiest option is to buy T-bills online using TreasuryDirect. If you're bidding competitively and you're new to Treasury bills, it's probably smart to work with a bank or broker.

The auction process begins as soon as the U.S. Treasury announces the Treasury bill auction. At this point, the Treasury starts accepting bids, which can be submitted until the auction closing time. The closing time is slightly different for competitive and noncompetitive bidders. In most auctions, the noncompetitive bids close at 12 p.m. (noon) Eastern time on closing day, and competitive bids close at 1 p.m.

In a single auction, an investor can buy a maximum of $10 million in bills through noncompetitive bidding. The maximum one investor can be awarded by competitive bidding is 35 percent of the total amount given out [source: TreasuryDirect].