Treasury Bills vs CDs for Short-Term Cash

A Treasury bill and a certificate of deposit are both safe, short-term parking spots for cash, but they differ sharply on taxes, liquidity, and insurance coverage. The choice hinges on how quickly you might need the money and your tax bracket.

The Basic Split

Treasury bills and CDs both promise you a known interest rate and your principal back on maturity. A Treasury bill is a short-term debt obligation of the U.S. government; when you buy one, you’re lending to the federal government for up to one year. A certificate of deposit is a contractual promise from a bank to pay a fixed rate if you lock money away for a set period.

The yields move in sync most of the time—both track short-term interest rates set by the Federal Reserve—but the tax treatment, liquidity, and early-exit costs diverge meaningfully for short-term investors.

After-Tax Yield: Where T-Bills Win

The most consequential difference is federal taxation. T-bills are exempt from state and local income tax. You pay federal income tax on the interest only; a resident of New York or California avoids the state levy entirely. A CD’s interest is fully taxable as ordinary income at the federal, state, and local level.

Concretely: suppose you’re in the 24% federal tax bracket plus 6% state tax. You buy a one-year T-bill yielding 4.5% and a one-year CD also yielding 4.5%.

The T-bill’s tax exemption is a permanent structural advantage, not a rate trick. Even if both are quoting the same nominal yield, the T-bill delivers more spendable dollars.

High-income investors and corporations often favor T-bills explicitly for this reason. In states with steep income taxes, the gap widens further.

Liquidity and the Secondary Market

T-bills trade on a large, active secondary market. If you need your cash back before maturity—say, three months into a six-month T-bill—you can sell it immediately. The price will reflect current interest rates; if rates have risen since you bought, you take a small loss; if they’ve fallen, you see a small gain.

CDs, by contrast, are illiquid by design. If you withdraw early, the bank typically charges a penalty—often three to six months of accrued interest, sometimes more. Some high-yield CDs have heftier penalties, and the terms vary widely by institution.

The practical implication: if you think you might need the cash before maturity, a T-bill is far more flexible. You don’t have to absorb a penalty; you simply sell. The secondary T-bill market is liquid enough that you’ll get a fair price within seconds.

A CD is best for cash you genuinely plan to leave untouched until maturity. If your time horizon is fuzzy, a T-bill reduces regret.

Safety and Insurance

Both vehicles are exceptionally safe, but through different mechanisms.

A T-bill is backed by the full faith and credit of the U.S. government. There is no insurance cap; the government will always pay you in full. Treasury-backed securities rank among the safest assets on Earth.

A CD is insured by the FDIC (Federal Deposit Insurance Corporation) up to $250,000 per depositor, per bank, per account type. If the bank fails, the FDIC makes you whole up to that ceiling. Most individuals’ CDs fall well within the cap, so the practical safety is equivalent to T-bills for typical deposit sizes.

If you’re parking $500,000 or more, the insurance limitation matters. You could split a mega-CD across multiple banks (each chunk under $250k) to preserve full FDIC coverage, but that’s friction. T-bills have no cap and require no splitting.

Rates and Maturities

T-bills are auctioned weekly for 4, 13, 26, and 52-week terms. The yields are whatever the market bids at auction; they move daily.

CDs come in many terms—3 months to 5 years is common—and each bank sets its own rate. Online banks typically offer higher rates than brick-and-mortar branches because they have lower overhead. Some banks offer custom maturity dates if you ask.

Both T-bill and CD yields tend to move together, tracking the Federal Reserve’s short-term policy rate. In a falling-rate environment, new T-bills and new CD rates decline in sync.

When to Choose Each

Reach for T-bills if:

• You’re in a high tax bracket (state income tax is meaningful to you)
• You might need the cash before maturity
• You’re parking more than $250k and want no insurance-cap headaches
• You value simplicity and want to avoid early-withdrawal penalty clauses

Reach for CDs if:

• You want a commitment device—locking funds away discourages dipping into them
• You’re in a low tax bracket where the state tax savings don’t matter much
• You prefer dealing with a single local bank for trust or convenience
• You like customizable maturity dates and terms

The Spread: Rates and Competitiveness

In normal circumstances, T-bill yields and CD yields track each other closely. When they diverge, online banks’ CDs often yield slightly more than T-bills, reflecting the CD’s illiquidity (you get paid for the lock-in). But that spread is typically thin—a quarter to half a percent—and can vanish if Treasury rates spike.

For very short time horizons (one to three months), T-bills are usually cheaper to access and more liquid. For four to twelve months, either works; your tax situation and liquidity needs should decide.

The Bottom Line

Both are respectable short-term homes for cash. T-bills win on after-tax yield and liquidity; CDs win on simplicity and the illusion of commitment. For most investors holding three to twelve months of expenses, a T-bill from a major brokerage (Schwab, Fidelity, Vanguard) or directly from Treasury Direct beats a CD once taxes are factored in. But if taxes are immaterial to you and you want the finality of a maturity date, CDs are perfectly sensible.

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