Treasury Bills vs. Money Market Funds in 2026: Which Cash Parking Option Delivers the Better After-Tax Yield?
A money market fund can make cash feel effortless: transfer money into a brokerage account, earn a competitive yield, and withdraw when needed. Treasury bills require more planning, but their state and local tax exemption can produce a better after-tax return—especially for investors in high-tax jurisdictions.
The right comparison is not simply the highest advertised rate. Investors should compare after-tax yield, liquidity, fees, maturity dates, and how quickly the investment’s rate will adjust if short-term interest rates change.
The Short Answer: Compare After-Tax Yield, Not the Headline Rate
Direct Treasury bills are often the stronger choice for cash tied to a known future expense. They provide a defined maturity date, very low U.S. government credit risk, and interest that is generally exempt from state and local income taxes.
Money market mutual funds are usually stronger for cash that must remain readily accessible. They can offer business-day liquidity, automatic reinvestment, and convenient integration with a brokerage account. Investors do not have to manage maturities or place recurring Treasury orders.
As an illustrative mid-2026 range, Treasury bill yields may be approximately 3.80% to 4.02%, while money market fund yields may fall broadly between 3.00% and 4.00%. These are estimates, not guaranteed rates. Both Treasury yields and fund yields can change as Federal Reserve policy, market expectations, and demand for short-term securities move.
The better option depends on four main variables:
- Your federal, state, and local marginal tax rates
- How long the money can remain invested
- Whether you need same-day or business-day access
- The fund’s expenses, holdings, minimum investment, and withdrawal rules
Treasury Bills vs. Money Market Funds: How Each Option Works
How Treasury bills work
Treasury bills, or T-bills, are short-term securities issued by the U.S. Department of the Treasury. Common terms include approximately three, six, and 12 months, although Treasury auctions also include other maturities.
T-bills do not make traditional coupon payments. Instead, an investor generally purchases a bill below its face value and receives the full face value at maturity. The difference represents the investor’s interest income.
For example, suppose an investor pays $9,810 for a T-bill with a $10,000 face value. If the bill is held to maturity, the Treasury pays $10,000. The $190 difference is the interest earned. The quoted annualized yield will depend on the purchase price, time to maturity, and yield-calculation convention.
T-bills can be purchased through TreasuryDirect or a brokerage firm. Brokerage accounts may make it easier to buy new issues, participate in automatic rollovers, or sell a bill before maturity.
How money market funds work
A money market fund is a mutual fund that pools investor assets and purchases short-term debt. Depending on its mandate, the portfolio may hold Treasury bills, U.S. government agency securities, repurchase agreements, commercial paper, certificates of deposit, or municipal obligations.
Most retail money market funds seek to maintain a stable net asset value of $1 per share. That objective makes them useful as cash-management vehicles, but the $1 value is not guaranteed.
Money market funds are securities, not bank deposits. They are generally not insured by the Federal Deposit Insurance Corporation. This distinction matters because a similarly named bank money market account is a deposit product that may qualify for FDIC insurance when held at an insured institution and within applicable limits.
2026 Yield Comparison: T-Bills, Taxable Funds, and Government Funds
The following table uses estimated mid-2026 ranges for illustration. Investors should obtain live quotes and current fund data before making a purchase.
| Cash option | Illustrative yield | Typical holdings | Liquidity | Tax treatment | Principal-value behavior |
|---|---|---|---|---|---|
| Direct Treasury bill | Approximately 3.80%–4.02% | Direct obligation of the U.S. Treasury | Cash at maturity; may be sold earlier through a brokerage | Federally taxable; generally exempt from state and local income tax | Face value paid at maturity; market price can fluctuate before maturity |
| Treasury money market fund | Approximately 3.00%–4.00% | Treasury securities and, depending on the fund, Treasury-backed repurchase agreements | Typically redeemable on business days, subject to fund and brokerage rules | Federally taxable; state exemption depends on qualifying holdings and state rules | Usually seeks a stable $1 share price, but it is not guaranteed |
| Government money market fund | Approximately 3.00%–4.00% | Treasuries, agency securities, and government-backed repurchase agreements | Typically business-day liquidity | Federally taxable; only part of the distribution may qualify for state exemption | Usually seeks a stable $1 share price, but it is not guaranteed |
| Taxable prime money market fund | Approximately 3.00%–4.00% | Commercial paper, CDs, bank obligations, Treasuries, and other short-term debt | Typically business-day liquidity, subject to applicable policies | Generally subject to federal, state, and local income taxes | May use a stable or floating share price depending on fund type |
Fund yields should be compared using the current seven-day SEC yield. This standardized figure annualizes the fund’s recent net income after expenses and is more useful than an old advertisement, a historical distribution rate, or a promotional APY from a different type of account.
The comparison still is not perfectly matched. A T-bill’s yield applies to a specific security and maturity. A money market fund’s seven-day yield reflects a portfolio that continually replaces maturing investments. The fund’s yield can therefore move up or down quickly as short-term market rates change.
How Taxes Change the Winner
T-bill interest is generally subject to federal income tax but exempt from state and local income taxes. High-income investors may also owe the 3.8% net investment income tax when applicable.
Distributions from a taxable money market fund are generally taxed as ordinary income. They may be subject to federal, state, and local taxes, as well as the net investment income tax for investors who meet the relevant income thresholds.
A simplified calculation is:
After-tax yield = stated yield × (1 − applicable marginal tax rate)
Consider an investor subject to a 32% federal rate, the 3.8% net investment income tax, and an 8.5% state or local rate. The applicable rate on Treasury interest would be 35.8%, while the combined rate on fully taxable fund income would be 44.3%.
Example: Comparing $100,000 of cash
A T-bill yielding 3.85% would produce an estimated after-tax yield of:
3.85% × (1 − 0.358) = 2.47%
On $100,000, that is approximately $2,472 of annualized after-tax income.
A taxable money market fund yielding 3.50% would produce:
3.50% × (1 − 0.443) = 1.95%
On $100,000, that is approximately $1,950 of annualized after-tax income. In this example, the T-bill provides about $522 more after tax over a full year, even before considering differences in compounding or changing fund yields.
An investor who lives in a state without an individual income tax would not receive the same state-tax advantage. In that situation, the headline yield, fund expenses, and access requirements may play a larger role.
Treasury and government money market funds require closer examination. A portion of a fund’s annual distribution may qualify for state tax exemption based on its qualifying U.S. government obligations. Repurchase agreements and agency securities may not receive the same treatment as direct Treasury obligations. Check the fund company’s annual tax supplement and your state’s rules rather than assuming the entire distribution is exempt.
Liquidity, Access, and Reinvestment Tradeoffs
T-bills provide certainty at maturity
A direct T-bill gives the investor a known maturity date and face value. That can work well for property taxes due in six months, tuition due next semester, or a home purchase planned for a specific month.
The tradeoff is reduced flexibility. Cash is committed until maturity unless the bill is sold through a brokerage. If market rates have risen since the purchase, the bill’s market value may be lower. If rates have fallen, it may sell for more. Holding to maturity avoids realizing those interim price changes, assuming the U.S. government makes the scheduled payment.
Money market funds simplify withdrawals
Money market funds typically permit redemptions on business days, making them practical for brokerage settlement cash and near-term expenses. Access is not necessarily instantaneous, however. Brokerage cutoff times, settlement procedures, bank-transfer timing, and fund-specific policies can determine when money becomes spendable.
Investors should verify whether a fund supports automatic liquidation for trades, check writing, debit access, or same-day transfers. “Liquid” does not always mean “available in a bank account immediately.”
Both options have reinvestment risk
A six-month T-bill locks in its yield only until maturity. If short-term rates fall, the proceeds may have to be reinvested at a lower yield. A money market fund faces the same economic issue because its manager continually replaces maturing holdings at current rates.
A T-bill ladder can spread this risk across several dates. For example, an investor with $40,000 might place $10,000 in bills maturing in roughly three, six, nine, and 12 months. As each bill matures, the investor can spend the proceeds or reinvest them.
The ladder requires tracking maturity dates, reinvesting proceeds, and managing cash left over when purchases do not use the entire account balance. A money market fund handles these tasks automatically, which is one reason its slightly lower after-tax yield may still be worthwhile.
Risk, Fees, and Account Protection
Direct T-bills carry very low credit risk because they are obligations of the U.S. government. When held to maturity, they also avoid the uncertainty of selling at a changing market price.
Money market funds add a pooled investment structure. Their risks can include portfolio credit exposure, interest-rate changes, fund-management decisions, operational issues, and liquidity pressure during periods of heavy redemptions. Government and Treasury funds generally avoid much of the private credit exposure found in prime funds, but they remain investment products.
Securities Investor Protection Corporation coverage is also frequently misunderstood. SIPC may protect customers if a SIPC-member brokerage fails and client securities or cash are missing, subject to statutory limits. It does not insure a promised yield, prevent a money market fund from losing value, or protect an investor from ordinary market losses.
Expense ratios matter because fund expenses reduce the return investors receive. The seven-day SEC yield is generally reported after fund expenses, but investors should still compare expense ratios, temporary fee waivers, minimum investments, trading charges, and brokerage service fees. A fee waiver can expire, reducing the fund’s future net yield.
Which Cash Parking Option Fits Your Situation?
Consider direct T-bills when:
- The money is earmarked for an expense with a known date.
- You can hold the security until maturity.
- You live in a high-tax state or municipality.
- You want direct U.S. Treasury exposure without a fund expense ratio.
- You are comfortable managing purchases, maturities, and reinvestment.
Consider a Treasury money market fund when:
- You want Treasury-focused exposure with easier withdrawals.
- The cash is used for brokerage trades or recurring transfers.
- You prefer automatic reinvestment and daily accruals.
- You have confirmed which portion of the fund’s income may qualify for state tax exemption.
Consider a taxable money market fund when:
- Immediate brokerage liquidity and convenience are the main priorities.
- The fund’s net yield compensates for its fees and tax treatment.
- You live in a low-tax or no-income-tax state.
- You understand the credit profile and redemption policies of the fund.
A blended approach can balance access and yield. An investor might keep one or two months of emergency expenses in a liquid money market fund while laddering T-bills for property taxes, tuition, estimated tax payments, or another dated obligation.
What to Do Next: A Practical Comparison Checklist
- Obtain the live T-bill yield for a maturity matching your cash deadline.
- Find each fund’s current seven-day SEC yield and expense ratio.
- Identify whether the fund is Treasury, government, prime, or municipal.
- Calculate the after-tax yield using your applicable federal, state, local, and net investment income tax rates.
- Review the fund’s annual tax information for the percentage of income attributable to qualifying Treasury obligations.
- Check investment minimums, purchase fees, brokerage commissions, and automatic-rollover options.
- Confirm redemption cutoff times, settlement timing, and bank-transfer delays.
- Match the maturity or liquidity terms to the date the money may be needed.
The bottom line is straightforward: direct T-bills often deliver the better after-tax yield for known-term cash, particularly in high-tax locations. Money market funds often deliver the better user experience for cash that must remain available and automated. Compare what you will keep after taxes and fees—not just the largest rate displayed on the screen.
This article is for educational purposes only and does not provide individualized investment, legal, or tax advice. Estimated 2026 yields can change. Consult current offering documents and, when appropriate, a qualified financial or tax professional before investing.