Guide

Treasury bills (T-bills) explained

When markets sell off and volatility spikes, investors often rotate toward cash. But cash is not one thing: money in a checking account, a high-yield savings account, a money market fund, and a U.S. Treasury bill all behave differently on yield, liquidity, credit risk, and taxes. Treasury bills (T-bills) are short-term debt obligations backed by the full faith and credit of the U.S. government, with maturities from four weeks to one year. They pay no periodic coupon; instead you buy them at a discount to face value and receive par at maturity. That simplicity, near-zero default risk, and state-tax exemption on interest make T-bills the benchmark for the risk-free short end of the yield curve — and a practical parking spot for dry powder between equity, bond, and crypto allocations.

What T-bills are — and what they are not

A T-bill is a zero-coupon government security. The U.S. Treasury auctions new bills weekly; once issued, they trade in a deep secondary market until they mature. Standard maturities include 4-week, 8-week, 13-week, 17-week, 26-week, and 52-week tenors. Bills differ from Treasury notes (2–10 years, semiannual coupons) and bonds (20–30 years) covered in our bonds and fixed income guide.

T-bills are not FDIC-insured bank deposits. They are direct claims on the U.S. government. In practice, T-bills are treated as the closest thing to a default-free dollar instrument in global finance — which is why their yields anchor pricing for money market funds, commercial paper, and the front end of the yield curve. They are also not inflation-protected: unlike TIPS, a T-bill's nominal return can lag realized inflation, a topic we return to when sizing cash against inflation hedges.

Discount pricing and yield math

Suppose you buy a 26-week T-bill with a $1,000 face value at a price of $975. You pay $975 today; in six months you receive $1,000. Your discount is $25 — that is your total return if held to maturity. There are no interim payments to reinvest, which simplifies accounting but means you have no coupon income along the way.

Quoted investment yield (bond-equivalent yield) annualizes that return on a 365-day basis so you can compare a 13-week bill to a 52-week bill or to a savings APY. The discount rate at auction is related but not identical to the yield you earn — Treasury publications and broker screens usually show both. Because price moves inversely with yield (as with all bonds), when the Fed keeps short rates elevated, newly auctioned T-bills come at steeper discounts and investors rolling maturing bills capture higher nominal yields.

Duration on a bill is tiny — a 3-month bill has far less interest-rate sensitivity than a 10-year note. That is the point: T-bills are a low-volatility cash proxy, not a bet on falling long-term rates. If you need duration exposure or income smoothing, notes, bond funds, or a barbell across maturities make more sense than stacking only ultra-short paper.

How auctions and the secondary market work

The Treasury sells new bills through competitive and noncompetitive auctions. Retail investors typically bid noncompetitive: you accept the high yield (or equivalently, the lowest price) determined by competitive bidders, and you are guaranteed allocation up to certain limits. Competitive bidders specify the yield they require; the auction clears at the marginal price.

You can participate directly at TreasuryDirect.gov with no intermediary markup, or buy in the secondary market through a brokerage. Secondary trading matters if you need to sell before maturity: you will receive the market price, which reflects current short rates and any day-count accrued discount. Liquidity is excellent for standard tenors, but selling early still introduces small price risk and spread costs — unlike a savings account where $1 nominally stays $1.

Laddering maturities

A common tactic is a T-bill ladder: stagger purchases across 4-, 8-, 13-, and 26-week maturities so something matures every few weeks. Each maturity rolls into a new auction yield, reducing reinvestment timing risk compared with putting everything into a single 52-week bill. Laddering pairs naturally with dollar-cost averaging discipline for equity contributions — cash flows from maturing bills fund periodic stock or fund purchases without trying to time the bottom.

T-bills vs savings accounts, CDs, and money market funds

The right cash vehicle depends on access, tax bracket, and how soon you need the money.

High-yield savings accounts offer daily liquidity and FDIC insurance on bank balances, but rates are set by the bank and can change without notice. Convenience is high; yield may lag auctioned T-bill rates when the front end of the curve is steep.
Certificates of deposit (CDs) lock a rate for a term with early-withdrawal penalties. They suit known horizons (a tuition bill in nine months) but sacrifice flexibility T-bills provide via the secondary market.
Money market funds hold very short government and corporate paper, passing through a variable yield. Government-only funds emphasize T-bill-like credit quality; prime funds add spread for slightly higher yield and slightly more complexity. Funds settle T+1 in many brokerages — fine for most investors, but not identical to instant ACH from a bank.
T-bills directly offer explicit government backing, transparent auction pricing, and state/local income tax exemption on interest (federal tax still applies). Setup friction is higher than clicking "transfer to savings."

None of these choices "wins" universally. Compare after-tax, after-fee yields at your marginal bracket, and match liquidity to the liability you are funding — emergency reserves, a known tax payment, or opportunistic dry powder for a market dislocation.

ETF and fund wrappers: SHV, BIL, SGOV, and money market ETFs

If you want T-bill economics inside a brokerage account without managing auctions, short Treasury ETFs and government money market funds are the usual wrappers. Tickers such as SHV, BIL, and SGOV (names and exact index rules change over time) hold baskets of very short Treasuries and roll maturities continuously. You buy and sell at market price like a stock; the fund handles auction participation and roll mechanics.

Trade-offs versus direct T-bills:

Expense ratios — typically a few basis points, but not zero.
Tracking drift — ETF net asset value can deviate slightly from underlying bill values intraday.
Tax reporting — fund distributions vs bill discount accrual may differ; consult your jurisdiction's rules.
Convenience — one-click rebalance between equities, bonds, and cash in the same account.

For large cash balances already at a custodian, wrappers often beat TreasuryDirect's operational overhead. For maximal yield on idle cash with willingness to ladder auctions, direct bills can edge ETFs by the fee spread.

Tax treatment and inflation reality

T-bill interest is taxable at the federal level as ordinary income in the year the bill matures (or when sold, if before maturity). A useful perk: that income is generally exempt from state and local income taxes in most states — a meaningful advantage for residents of high-tax jurisdictions compared with fully taxable savings interest or corporate money market income.

Nominal yield is not real yield. If a 13-week bill auctions at 4.5% and CPI runs hotter, your purchasing power still erodes. T-bills protect against default and short-term volatility, not sustained inflation. Investors worried about purchasing power often pair a cash/T-bill sleeve with TIPS, I-bonds (when available), or growth assets — see our inflation hedging guide for the full toolkit. Ahead of CPI releases and Fed meetings, front-end yields can move sharply; that is market pricing of near-term policy, not a guarantee of future real returns.

Where T-bills fit in a portfolio

T-bills are the cash and near-cash layer — not a substitute for diversified equities or intermediate bonds. Typical roles:

Emergency reserve — 3–6 months of expenses in liquid, low-volatility form; laddered bills or a government money market fund.
Rebalancing dry powder — after a drawdown, maturing bills fund equity purchases without selling other assets at lows.
Known liabilities — property taxes, tuition, or a home down payment within 12 months; match maturity to the due date.
Volatility buffer in multi-asset accounts — reduce margin stress and forced selling when crypto or equities gap down.

Oversizing cash feels safe emotionally but has an opportunity cost: long horizons still favor productive assets. Undersizing cash forces liquidation at bad prices. A explicit policy — "I keep X months in T-bills or equivalent, rebalance when equities exceed Y% of net worth" — beats reacting to headlines.

Risks and misconceptions

"Risk-free" means no volatility ever." Bill prices still fluctuate before maturity; only hold-to-maturity eliminates mark-to-market swings.
Reinvestment risk. When bills mature, new auctions may offer lower yields if the Fed cuts — laddering mitigates but does not remove this.
Operational limits. TreasuryDirect has account quirks and transfer timing; plan ahead of large purchases.
Confusing bills with stablecoins. Tokenized "T-bill" products on crypto rails carry wrapper, custody, and regulatory risks beyond holding Treasuries at a regulated custodian.
Chasing the last 10 basis points. Yield differences between competitive savings, ETFs, and direct bills are often smaller than behavioral mistakes — panic selling risk assets for marginal cash yield.

Practical checklist

Define the job — emergency liquidity, scheduled expense, or strategic dry powder; match maturity and account type.
Compare after-tax yields — include state tax exemption for T-bills vs fully taxable bank interest at your bracket.
Choose access path — TreasuryDirect ladder, brokerage secondary market, or ETF/money market fund based on size and friction.
Ladder if rolling frequently — stagger 4- to 26-week maturities to smooth reinvestment.
Pair with a rebalance rule — pre-commit how maturing cash deploys into equities or bonds.
Revisit when the curve moves — inversion or steepening at the front end changes relative attractiveness vs longer fixed income.
Do not confuse nominal yield with inflation protection — size TIPS or real assets separately if purchasing power is the goal.

Key takeaways

T-bills are short, zero-coupon U.S. government debt sold at a discount and redeemed at par.
Auctions set yields weekly; laddering maturities reduces reinvestment timing risk.
State tax exemption can make T-bills attractive versus taxable savings for high-bracket investors.
ETFs and money market funds wrap the same economics with convenience and small fees.
T-bills stabilize portfolios — they do not replace growth assets or inflation hedges.
Compare after-tax, after-fee yields and match liquidity to the liability you are funding.