Treasury Bill

T-bills are issued by the U.S. Department of the Treasury and are backed by the full faith and credit of the U.S. government, making them widely regarded as the world's safest short-term investment. They are sold in denominations starting at $100 and come in standard maturities of 4 weeks, 8 weeks, 13 weeks (3 months), 17 weeks, 26 weeks (6 months), and 52 weeks (1 year). T-bills are auctioned weekly by the Treasury through TreasuryDirect.gov and are also actively traded in the secondary market.

Unlike bonds, T-bills pay no periodic coupon. Instead, they are sold at a price below their $1,000 face value. For example, you might pay $980 for a 26-week T-bill that matures at $1,000, earning $20 in profit — a yield of roughly 4.1% annualized. This 'discount pricing' method is a defining characteristic of short-term government paper.

T-bill yields function as a cornerstone of financial markets. The 3-month T-bill yield is widely used as a proxy for the 'risk-free rate' in financial models such as the Capital Asset Pricing Model (CAPM) and the Sharpe ratio. When T-bill yields are high, they compete directly with stocks for investor capital — a dynamic that became especially relevant in 2022–2023, when 6-month T-bills briefly yielded more than 5.5%, making the old '4% safe withdrawal rule' look attractive compared to the volatility of equities.

During the 2008 financial crisis, demand for T-bills was so intense — driven by a 'flight to safety' — that yields briefly went negative in December 2008, meaning investors were willing to pay more than face value just to guarantee their capital was in U.S. government paper. This extraordinary episode underscored T-bills' status as the ultimate safe haven in times of market panic.

For retail investors, T-bills purchased through TreasuryDirect are exempt from state and local income taxes, though they are subject to federal income tax, making them particularly attractive to high-earners in states with high income taxes like California or New York.

T-Bill Auctions: The U.S. Treasury sells T-bills through a competitive auction process conducted by the Federal Reserve on the Treasury's behalf. Most retail investors participate through TreasuryDirect.gov using a 'noncompetitive bid,' which guarantees they receive the full amount of T-bills requested at the yield determined by the competitive bidding process — meaning retail buyers are price takers who accept whatever yield the institutional market establishes. Competitive bids, used by banks, dealers, and large institutions, specify both a desired yield and a quantity; only bids at or below the stop-out rate (the highest yield accepted by the Treasury) are awarded. Auctions for different T-bill maturities occur on regular weekly or monthly schedules: 4-week, 8-week, and 17-week bills are typically auctioned weekly, while 13-week and 26-week bills are auctioned every Monday. Settlement generally occurs one business day after the auction. Investors who purchase T-bills on the secondary market through a brokerage account face the same economics but pay a bid-ask spread to a dealer rather than participating directly in the auction.

T-Bills as Cash Equivalent: In financial accounting and investment management, T-bills with maturities of three months or less are classified as cash equivalents on corporate balance sheets — instruments so liquid and credit-risk-free that they are treated as functionally equivalent to cash. Warren Buffett's Berkshire Hathaway, for example, holds tens of billions of dollars in T-bills as its primary cash reserve, reflecting both the credit quality and the immediate liquidity the instruments provide. For retail and institutional investors, T-bills serve as a yield-bearing parking place for capital that may be needed on short notice but does not need to be deployed into longer-duration or riskier assets. During the 2022–2023 high-rate environment, the attractiveness of 5%-plus T-bill yields — with essentially no credit risk and full state and local tax exemption — led to a significant shift of household and institutional cash from bank savings accounts and money market funds directly into T-bills.