Treasury Bills vs High-Yield Savings Accounts: Which Pays More After Taxes?

Reviewed by the Prime Rate Editorial Team

The question behind “treasury bills vs savings account” feels urgent when you glance at yields. In late October 2025, both four‑week T‑bills and competitive online savings accounts are offering north of 4%, a welcome reversal from the near‑zero rates savers endured a few years ago. A 4.29% high rate on the most recent four‑week bill, according to TreasuryDirect’s auction results, looks nearly identical to the 4.20% APY that NerdWallet’s October 2025 survey of top high‑yield savings accounts was showing. The gap is small enough that many people assume the choice doesn’t matter, and that’s exactly where they lose money.

This article is for anyone holding cash they don’t need tomorrow but also don’t want to lock up for years. What makes the T‑bill recommendation work is the interaction between yield and tax code; what can make it fail is the friction of buying, holding, and reinvesting short‑term government debt when a savings account is a single tap away.

What T‑Bills and Savings Accounts Are Yielding Right Now

Right now, the 4‑week T‑bill auctions around 4.29% and the 8‑week bill at about 4.20%, according to TreasuryDirect’s late‑October 2025 auction results. Top‑tier high‑yield savings accounts sit just below that, at 4.20% APY, based on NerdWallet’s daily rate tracking. The spread is thin, only about nine basis points, but the direction matters: the T‑bill, not the bank, is offering the higher simple interest rate before we even talk about taxes.

What’s different this time is the backdrop of falling rates. The Federal Reserve has already delivered multiple cuts from its cycle peak, and both T‑bill yields and HYSA APYs are drifting down together. When the prime rate drops, savings account rates typically follow within a month; T‑bills reprice instantly at each auction. That means rate‑chasing with HYSAs, jumping from one promotional APY to another, becomes a frustrating game of diminishing returns, while a T‑bill ladder locks your rate for each rung. I’ve watched readers burn hours chasing an extra 10 basis points only to have the new bank cut its rate three weeks later. If you’re weighing CD rates vs high‑yield savings for a slightly longer horizon, you’ll see the same dynamic: guaranteed yields beat floating ones when the trend is downward. Understanding what happens to your savings when the prime rate rises or falls can help you anticipate when that dynamic is likely to shift again.

How Taxes Treat T‑Bill Interest vs HYSA Interest, and the State‑Tax Edge

Both T‑bill interest and HYSA interest are taxed as ordinary income at the federal level, so there’s no free lunch with the IRS. The twist is the state‑tax exemption. Interest earned on Treasury securities, whether bills, notes, or bonds, is exempt from state and local income taxes under 31 U.S.C. § 3124, while savings account interest gets hit by every layer of tax. In a high‑tax state like California, New York, or New Jersey, that single exemption can quietly convert a modest pre‑tax advantage into a wide after‑tax lead.

The mechanics are straightforward. If you earn $1,000 of HYSA interest in a year, that $1,000 gets added to your federal gross income and your state taxable income. The same $1,000 earned from a four‑week T‑bill only shows up on your federal return. A California resident in the 24% federal bracket and a 9.3% state bracket would hand over $333 in combined taxes on the HYSA interest versus just $240 on the T‑bill interest, a $93 difference on that $1,000. Scale that across a $50,000 cash position, and the gap is $465 a year. That’s real money for doing nothing except choosing a different parking spot.

What often catches savers off guard is that the exemption works regardless of whether you hold the T‑bill in a TreasuryDirect account or a brokerage. The tax treatment attaches to the security, not the platform. Per IRS Publication 550, interest on obligations of the United States is exempt from state and local taxation. That insight points beyond just bills: Treasury bonds, notes, and even TIPS share the same state‑tax shield. For the 4‑ to 13‑week money that most closely resembles a savings account substitute, short‑term T‑bills match the time horizon while dodging the state‑tax bill. If you’re also thinking about tax-advantaged accounts as part of a broader cash management strategy, reviewing IRA contribution limits for 2026 can help you understand how much room you have to shelter other income from tax entirely.

When State Taxes Flip the Winner: After‑Tax Yield Math

The raw numbers erase any doubt. I ran the after‑tax yields for a 24% federal bracket at four state‑tax levels using the October 2025 yields of 4.29% for the T‑bill and 4.20% APY for the HYSA. Even with zero state tax, the T‑bill still comes out ahead, and the advantage only grows as the state rate climbs.

There is no break‑even state tax rate where the HYSA catches up, because the T‑bill already pays more pre‑tax. For a zero‑tax state resident, the difference is tiny, 0.07% on the top line, or about $7 per $10,000, but for anyone paying even a moderate state income tax, the margin is material enough that you shouldn’t ignore it.

Liquidity, Access, and Why It Matters for Emergency Savings

The single strongest argument for an HYSA over a T‑bill isn’t yield, it’s access. When an unexpected bill lands or an emergency expense arrives, a high‑yield savings account lets you transfer funds instantly to your checking account. A T‑bill, by contrast, is locked until its maturity date unless you choose to sell it early on the secondary market, where the price you receive depends on current interest rates and the demand that day. If rates have risen since you purchased the bill, you could receive less than face value. That liquidity gap matters enormously for anyone whose cash position doubles as an emergency fund.

The practical workaround is segmentation. Rather than choosing between a T‑bill and a HYSA as an all‑or‑nothing decision, many savers split their cash reserves: one to two months of expenses stay in the HYSA for instant access, while anything beyond that threshold gets allocated to rolling T‑bills. A 4‑week or 8‑week ladder keeps maturing funds cycling back every month, which means you rarely have to wait long for liquidity even if an unexpected cost exceeds your HYSA cushion. If you want to understand how to apply the same laddering logic to longer‑duration instruments, our guide on what a CD ladder is and how to build one walks through the mechanics in detail, the principles transfer almost directly to T‑bills.

It’s also worth distinguishing between T‑bills held at TreasuryDirect and those held through a brokerage. TreasuryDirect does not allow you to sell before maturity; the only exit is waiting. A brokerage account, Fidelity, Schwab, or Vanguard, for example, gives you secondary‑market access during business hours, which partially restores liquidity. For savers who want the tax benefit but don’t want to be fully locked in, holding T‑bills in a brokerage is the better structural choice. And if you’re weighing a money market account as a middle ground, note that money market funds that invest primarily in Treasuries often pass through a partial state‑tax exemption as well, though the percentage varies by fund and year.

Who Should Choose a T‑Bill and Who Should Stick With the HYSA

There is no universally correct answer in the treasury bills vs savings account debate, because the right choice depends on three variables that vary by person: your state tax rate, your cash timeline, and your tolerance for administrative friction.

T‑bills make the most sense if you:

• Live in a state with an income tax of 4% or higher, the exemption is where most of the after‑tax advantage accumulates.
• Are holding cash you won’t need for at least four weeks and can plan your spending around a predictable maturity schedule.
• Have more than $250,000 in cash that would exceed FDIC limits at a single bank, T‑bills sidestep the coverage ceiling entirely.
• Are comfortable opening a TreasuryDirect account or already have a brokerage that supports Treasury purchases.
• Want to lock in today’s rate before the next Fed cut reprices HYSA yields lower.

The HYSA is the better choice if you:

• Live in a state with no income tax (Florida, Texas, Nevada, and six others), the T‑bill’s after‑tax edge shrinks to roughly seven basis points at current yields, which is unlikely to justify the added friction.
• Need genuine on‑demand liquidity, your cash reserve is also your emergency fund and you can’t predict when you’ll need it.
• Are new to fixed‑income investing and find the auction process or brokerage mechanics confusing enough to cause errors.
• Hold a balance small enough that the dollar difference is immaterial, on $5,000, even a 0.46% after‑tax advantage is only $23 a year.

One nuance worth naming: even readers who should choose T‑bills often benefit from maintaining a small HYSA balance rather than eliminating it. The operational simplicity of having a few thousand dollars in instant‑access cash is worth something, and it prevents you from having to liquidate a T‑bill at an inopportune moment. If you’re also thinking through your broader savings architecture, where retirement accounts, taxable investments, and liquid reserves all fit together, comparing a Roth IRA vs Traditional IRA is worth doing in parallel, since the tax treatment of those accounts intersects with where you want to park short‑term cash.

How to Actually Buy a T‑Bill: TreasuryDirect vs Brokerage

Knowing the math is only half the job. The other half is executing the purchase, and the friction here is real enough that it stops some savers from acting. There are two main routes: TreasuryDirect and a brokerage account.

TreasuryDirect is the U.S. government’s own platform at TreasuryDirect.gov. You open a free account, link a bank account, and schedule a purchase at the next weekly auction. Four‑week bills auction every Tuesday and settle on Thursday. The minimum purchase is $100, and the interface, while dated, is functional. The major limitation is that there is no secondary market: once you’ve bought, you hold to maturity. TreasuryDirect is best for buyers who genuinely plan to hold to maturity and want direct government ownership without any brokerage layer.

Brokerage accounts at Fidelity, Schwab, or Vanguard let you buy T‑bills either at auction (no commission) or on the secondary market. The auction process mirrors TreasuryDirect in most respects, but the key difference is that you can sell before maturity through the brokerage’s bond desk if your circumstances change. Brokerage T‑bills also show up on a single consolidated statement, which simplifies tax reporting, your 1099‑INT will already break out the Treasury interest so your tax software can flag the state exemption.

For most readers who are new to this, I recommend starting with a brokerage account you already have rather than opening a separate TreasuryDirect account. The marginal convenience of direct Treasury ownership is small, and the flexibility of being able to sell early is worth more than it sounds when life gets unpredictable. A brief note on settlement: T‑bills purchased at auction typically settle two business days after the auction date, so your funds are not earning the T‑bill rate during that brief window, a small but real consideration if you’re moving money from a same‑day HYSA.

Case Study: A $25,000 Cash Reserve in California

To make the numbers concrete, consider a composite reader: a freelance designer in Los Angeles with a $25,000 cash reserve. She’s in the 22% federal bracket and California’s 9.3% state bracket. She currently keeps everything in an online HYSA at 4.20% APY. Her annual interest income is roughly $1,050.

After federal tax at 22%, she keeps $819. California then takes 9.3% of the same $1,050, costing her another $98. Her net after‑tax yield is approximately $721, or 2.88% on the $25,000.

If instead she moves $20,000 into rolling 4‑week T‑bills (keeping $5,000 in the HYSA for instant access), the T‑bill portion earns approximately $858 in gross interest annually at 4.29%. After 22% federal tax, she keeps $669, and pays zero California tax. The HYSA portion earns $210 gross, nets to $164 after combined federal and state tax. Her total after‑tax interest: $833, compared to $721 with the all‑HYSA approach. That’s a $112 improvement with no change in risk and only a one‑time setup cost of about 20 minutes to open or configure a brokerage account for T‑bill purchases.

That $112 is not life‑changing, but it compounds. Over five years, assuming rates stay flat and she reinvests, the cumulative after‑tax difference exceeds $600. More importantly, the structural habit of segmenting liquid cash from near‑liquid cash tends to improve saving behavior overall, readers who set up the T‑bill ladder report being less tempted to dip into the near‑liquid portion for discretionary spending, which is a behavioral dividend on top of the financial one. Getting that financial foundation right pairs well with other cash‑flow decisions; if you haven’t mapped out your income and expenses recently, working through how to create a monthly budget that actually works can clarify exactly how much of your cash reserve is truly idle and eligible for a T‑bill allocation.

Action Plan: Steps to Capture the T‑Bill Advantage

1. Check your state income tax rate. If your state taxes ordinary income at 4% or more, the T‑bill’s state‑tax exemption is meaningful enough to act on. Residents of zero‑tax states can skip to step 5 and decide whether the pre‑tax spread alone justifies the extra steps.
2. Separate your emergency fund from your optimization fund. Decide how many months of expenses you need in instant‑access cash. That portion stays in the HYSA. Everything above that threshold is a candidate for T‑bills.
3. Open or confirm brokerage access for Treasuries. If you already have a Fidelity, Schwab, or Vanguard account, verify you can buy Treasuries at auction, most standard accounts can. If not, TreasuryDirect takes about 10 minutes to set up with a Social Security number and bank account number.
4. Place your first auction order. For a 4‑week bill, the auction typically runs Tuesday morning with results by noon. Submit a noncompetitive bid (you accept the auction‑determined rate) for whatever amount you’ve designated. Settlement follows on Thursday.
5. Set up auto‑reinvestment if you plan to roll continuously. TreasuryDirect allows you to schedule automatic reinvestment for up to two years. Most brokerages require you to manually reinvest at maturity, which adds a step but gives you the option to redirect funds if your cash needs change.
6. Track the interest on your tax return. Treasury interest appears on Form 1099‑INT in Box 3, labeled “Interest on U.S. Savings Bonds and Treas. Obligations.” Most tax software (TurboTax, H&R Block) automatically excludes this from your state return when you enter the 1099‑INT correctly. Confirm your software is doing so, the error is common and easy to catch.
7. Reassess when rates shift significantly. If T‑bill yields drop below HYSA APYs, which can happen briefly after aggressive Fed cuts, the math may temporarily favor the HYSA even in high‑tax states. Monitor quarterly rather than weekly; overreaction to small rate moves costs more in friction than it saves in yield.

Frequently Asked Questions

Are Treasury bills really safer than a high‑yield savings account?

Both are extremely low‑risk, but they carry different types of safety guarantees. High‑yield savings accounts at FDIC‑member banks are insured up to $250,000 per depositor per ownership category, meaning the federal government reimburses you if the bank fails. Treasury bills are backed by the full faith and credit of the U.S. government itself, they are direct obligations of the Treasury, not a deposit insurance backstop. In practice, both are considered as close to risk‑free as any financial instrument gets. The distinction matters primarily for balances above $250,000: T‑bills have no cap, while HYSA holders above the FDIC limit carry bank‑failure risk on the excess unless they spread deposits across multiple institutions.

Do T‑bills beat savings accounts after taxes in every state?

At October 2025 yield levels, yes, but the margin varies significantly. In zero‑tax states like Florida, Texas, and Nevada, the T‑bill’s after‑tax advantage shrinks to roughly 0.07 percentage points (about $7 per $10,000 annually), which many savers will reasonably decide isn’t worth the added setup. In high‑tax states like California, New York, and New Jersey, the after‑tax gap widens to 0.46%–0.96% depending on the bracket, a meaningful difference on any balance above $10,000. The T‑bill wins in every state because it also pays more pre‑tax, but the case is strongest where state income taxes are highest.

What happens to my T‑bill if I need the money before it matures?

If you hold the T‑bill through TreasuryDirect, you cannot sell before maturity, you must wait for the bill to mature and the funds to return to your linked bank account. If you hold T‑bills through a brokerage account such as Fidelity, Schwab, or Vanguard, you can sell on the secondary market during business hours. The price you receive will be based on current market rates: if interest rates have risen since you purchased the bill, you may receive slightly less than face value. For a 4‑week bill purchased just days ago, that price risk is minimal. For longer maturities held when rates move sharply, the loss could be more noticeable, though still small in absolute terms compared to equities.

How do I report T‑bill interest on my tax return?

Your broker or TreasuryDirect will send you a Form 1099‑INT each January for the prior tax year. Treasury interest appears in Box 3, labeled “Interest on U.S. Savings Bonds and Treas. Obligations.” When you enter this 1099‑INT into tax software like TurboTax or H&R Block, the program should automatically exclude the Box 3 amount from your state taxable income. It’s worth confirming this is happening correctly, search your state return for “Treasury” or “U.S. obligations” to verify the subtraction is appearing. If you file with a CPA, flag the Box 3 amount explicitly; the exclusion is easy to apply correctly but also easy to overlook if your preparer is working quickly.

Can I buy T‑bills inside a Roth IRA or Traditional IRA?

Yes, most brokerage IRAs allow you to purchase Treasury bills just as you would in a taxable account. However, the state‑tax exemption that makes T‑bills so attractive in taxable accounts is irrelevant inside an IRA, all earnings inside the account grow tax‑deferred (Traditional IRA) or tax‑free (Roth IRA) regardless of what you invest in. That means the T‑bill vs. HYSA comparison inside an IRA is purely a yield question, not a tax question. At October 2025 rates, the T‑bill still pays slightly more pre‑tax, so it may still be the better parking spot for short‑term IRA cash waiting to be deployed, but the urgency is lower than in a taxable account.

What is the minimum amount needed to invest in a T‑bill?

Treasury bills purchased through TreasuryDirect or a brokerage have a minimum purchase of $100, with additional increments of $100. This is significantly lower than many people assume, and it means the T‑bill strategy is accessible even to savers who aren’t holding large cash reserves. The administrative overhead of setting up an account and scheduling auction purchases is essentially fixed regardless of your balance size, so the strategy makes the most economic sense for balances where the dollar difference in after‑tax yield justifies the one‑time setup. On $1,000, the annual advantage over a HYSA in a high‑tax state is roughly $5–$10; on $20,000, it’s $90–$190.

How often do T‑bill auctions happen, and how long does it take to get started?

Four‑week and 8‑week T‑bills auction every Tuesday, with results announced the same day and settlement (when your cash leaves and the bill is credited) occurring on the following Thursday. Thirteen‑week bills also auction weekly. The process of opening a TreasuryDirect account typically takes 10–15 minutes if you have your Social Security number and bank account details handy, though account verification can take a few business days before your first purchase. Brokerage accounts you already have may allow T‑bill purchases immediately. From the moment you decide to act to the moment your first T‑bill is held can be as short as one week, making this a genuinely quick transition from a HYSA for most savers.

Are there T‑bill ETFs or mutual funds that offer similar tax benefits without the auction process?

Yes. Funds like the iShares 0‑3 Month Treasury Bond ETF (SGOV) or the SPDR Bloomberg 1‑3 Month T‑Bill ETF (BIL) invest exclusively in short‑term Treasury securities and pass through the state‑tax exemption proportionally based on the percentage of fund assets held in U.S. government obligations. The percentage varies year to year and is disclosed in the fund’s annual tax supplement. For most years, 99%–100% of these funds’ income qualifies for the state exemption. The trade‑off is that ETFs trade on an exchange, so their yield slightly underperforms direct T‑bill ownership due to the expense ratio (SGOV charges 0.09% annually). For savers who want near‑zero friction, a T‑bill ETF in an existing brokerage account splits the difference between a HYSA and direct Treasury ownership.

Does the T‑bill advantage hold if the Federal Reserve cuts rates further?

The pre‑tax yield comparison will shift as rates move, if T‑bill yields fall faster than HYSA APYs, the pre‑tax spread could temporarily favor the savings account. However, the state‑tax exemption is a structural feature that doesn’t disappear with rate cuts; it widens or narrows only as your state tax bracket changes. At present yields, even a 25‑basis‑point drop in T‑bill yields (to roughly 4.04%) while HYSAs stay at 4.20% would still favor the T‑bill on an after‑tax basis in any state with an income tax above about 2%. The strategy requires monitoring, check quarterly and compare after‑tax yields using your actual brackets, but it doesn’t need constant management. Tracking broader CD rate forecasts for 2026 can give you a useful proxy for where T‑bill yields are likely headed.

How does the T‑bill vs. HYSA comparison change for someone in a lower tax bracket?

The lower your federal bracket, the smaller the absolute tax savings, but the state‑tax exemption remains proportionally valuable. A saver in the 12% federal bracket with a 5% state tax rate sees