According to Federal Reserve macroeconomic balance sheet data, more than $6.8 trillion in American consumer cash remains parked in commercial bank high-yield savings accounts (HYSAs) earning nominal yields between 4.00% and 4.75% APY.
However, interest earned from private bank deposits is fully taxable as ordinary income at both the federal and state level, causing savers residing in high-tax jurisdictions like California, New York, New Jersey, and Massachusetts to surrender up to 13.3% of their nominal interest to state tax authorities.
Under Title 31 of the United States Code (31 U.S.C. § 3124), short-term United States Treasury Bills (T-Bills) are completely exempt from all state and local income taxes, delivering an effective tax-equivalent yield of 5.50% to 6.20% with zero credit default risk and superior liquidity.
The 30-Second Cash Allocation Summary
If you live in a state with moderate to high personal income taxes (California, New York, New Jersey, Oregon, Minnesota, or Massachusetts), keeping cash in an online bank savings account is financially sub-optimal.
United States Treasury Bills are short-term government debt obligations maturing in 4, 8, 13, 17, 26, or 52 weeks, backed by the full faith and credit of the federal government.
By purchasing T-Bills directly through your existing Fidelity, Schwab, or Vanguard brokerage accounts, you capture higher nominal yields while legally erasing state and city income taxes on every penny of earned interest.
| State of Residence | Top State Marginal Tax Rate | Bank HYSA Nominal Yield (4.50% APY, illustrative) | 13-Week T-Bill Nominal Yield (5.20%, illustrative) | T-Bill State Tax-Equivalent Yield (STEY) |
|---|---|---|---|---|
| California | 9.30% to 13.30% | 4.50% Gross (3.90% Net State) | 5.20% Net State | 5.73% to 6.00% Equivalent |
| New York City (NY State + City) | 10.90% + 3.87% (14.77% Total) | 4.50% Gross (3.83% Net State/City) | 5.20% Net State/City | 6.10% Equivalent Yield |
| New Jersey | 6.37% to 10.75% | 4.50% Gross (4.01% Net State) | 5.20% Net State | 5.55% to 5.82% Equivalent |
| Massachusetts | 5.00% to 9.00% (Sur-tax) | 4.50% Gross (4.09% Net State) | 5.20% Net State | 5.47% to 5.71% Equivalent |
| Texas / Florida (Zero Tax) | 0.00% State Tax | 4.50% Gross | 5.20% Gross | 5.20% (Pure Nominal Spread) |
The Statutory and Mathematical Engine: 31 U.S.C. § 3124
The constitutional framework that shields Treasury obligations from state taxation dates back to the landmark 1819 Supreme Court ruling in McCulloch v. Maryland, which established that states cannot tax federal debt instruments.
This doctrine is formally codified under Title 31 of the United States Code, Section 3124(a):
“Stocks and obligations of the United States Government are exempt from taxation by a State or political subdivision of a State. The exemption applies to each form of taxation that would require the obligation, the interest on the obligation, or both, to be considered in computing a tax.”
To compare a state-tax-exempt Treasury Bill against a fully taxable commercial bank account, financial analysts utilize the State Tax-Equivalent Yield (STEY) formula:
State Tax-Equivalent Yield (STEY) Formula
STEY = T-Bill Nominal Yield ÷ (1 − State Marginal Tax Rate)
Consider an investor residing in San Francisco, California, facing a marginal state tax bracket of 10.3%.
If a 13-week T-Bill yields a nominal 5.25% (an illustrative rate; check TreasuryDirect for current auction results), the calculation is:
STEY = 5.25% ÷ (1 − 0.103) = 5.25% ÷ 0.897 = 5.85%
For a California bank savings account to deliver the same after-tax cash return as that 5.25% T-Bill, the bank would need to advertise a staggering 5.85% APY: a rate that no commercial banking institution in the United States currently offers.
The mathematical advantage expands even further in jurisdictions that enforce local municipal income taxes on top of state rates.
Residents of New York City face a top state tax of 10.9% combined with a local NYC resident tax of 3.876%, pushing total local tax drag to 14.776%.
In Yonkers, New York, residents pay a 16.75% surcharge on their state tax liability. In Maryland, county income taxes add another 2.25% to 3.20% to state brackets.
Because 31 U.S.C. § 3124 explicitly commands that Treasury obligations are exempt from “taxation by a State or political subdivision of a State,” every city, county, and municipal surcharge is completely neutralized.
The 5-Step Rolling T-Bill Ladder Playbook
A common objection to Treasury Bills is that funds are locked until maturity. This concern is completely eliminated by structuring an automated rolling T-Bill ladder.
Step 1: Divide Cash Reserves into Four Equal Tranches
Take your emergency fund or cash reserves (e.g., $40,000) and segment the capital into four equal $10,000 blocks.
You will deploy these four tranches across four consecutive weekly Treasury auctions, establishing a rolling liquidity cycle.
Step 2: Enter Non-Competitive Auction Bids via Brokerage
Log into your Fidelity, Charles Schwab, or Vanguard brokerage account and navigate to the “Fixed Income & Bonds” trade tab.
Select “Treasury Auctions” and choose the 4-week or 13-week T-Bill. Enter a “Non-Competitive Bid” for the first $10,000 tranche.
Non-competitive bidding guarantees your order is filled at the average clearing auction yield set by institutional primary dealers.
Step 3: Stagger Purchases Over Four Consecutive Weeks
During Week 1, purchase Tranche A (4-week T-Bill). During Week 2, purchase Tranche B (4-week T-Bill).
Repeat for Tranche C in Week 3, and Tranche D in Week 4.
Once fully deployed, exactly one tranche ($10,000) matures every single Thursday, providing continuous weekly liquidity.
Step 4: Enable Automated Reinvestment (“Auto-Roll”)
Check the “Auto-Roll” or “Automatic Reinvestment” box during order placement.
When Tranche A matures on Thursday morning, the principal automatically rolls into the subsequent 4-week auction, while your accrued interest is deposited directly into your cash core sweep account.
Step 5: Access Capital in One Click Without Waiting
If an unexpected financial emergency arises and you need immediate cash before a T-Bill matures, you do not need to wait for Thursday.
Because Treasury Bills trade in the most liquid secondary bond market in the world, you can sell your T-Bill on the secondary market inside your brokerage dashboard in two seconds during market hours with negligible bid-ask spreads.
Brokerage Platforms vs TreasuryDirect: Why You Should Avoid the Government Website
Many retail investors search for Treasury Bills and end up creating accounts on TreasuryDirect.gov, the official web portal operated by the Bureau of the Fiscal Service.
While functional, TreasuryDirect is plagued by outdated 1990s web architecture, clumsy password navigation rules, and severe liquidity bottlenecks.
Most critically, TreasuryDirect does not maintain a secondary trading marketplace.
If you purchase a 26-week T-Bill on TreasuryDirect and need your cash in an emergency three months later, you cannot sell the bond online.
You must fill out paper Form FS Form 5512, obtain an official medallion signature guarantee at a physical bank branch, and mail the paper forms to the Treasury to transfer the bond to an outside broker: a process that takes six to eight weeks.
By purchasing Treasury Bills directly through private brokerages like Fidelity or Schwab, you enjoy commission-free trades, auto-roll capabilities, consolidated annual 1099 tax reporting, and instant same-day secondary market liquidity.
Illustrative State Tax Scenarios
This is a hypothetical example, not a real person or measured result.
Scenario A: The California HYSA Trap
Robert kept a $150,000 cash down payment fund in an online high-yield savings account yielding 4.50% APY.
Over twelve months, his savings account paid him $6,750 in gross interest.
Because Robert lived in Los Angeles and earned a solid income as a software engineer, his marginal state tax rate was 10.3%.
At tax time, Robert had to pay $695.25 directly to the California Franchise Tax Board on his savings interest, in addition to federal taxes.
His effective net yield after state taxes fell to just 4.03%.
Scenario B: The New York T-Bill Ladder Strategist
Elena lived in Manhattan and maintained an identical $150,000 cash reserve. She structured a rolling 13-week Treasury Bill ladder via Fidelity yielding 5.25%.
Her T-Bill portfolio generated $7,875 in gross interest across the year.
Under 31 U.S.C. § 3124, Elena’s entire $7,875 was completely exempt from New York State income tax (6.85%) and New York City local tax (3.87%).
By choosing T-Bills over a bank savings account, Elena legally bypassed $844.20 in state and municipal taxes while capturing $1,125.00 in higher nominal interest, netting an extra $1,969.20 in cash in her pocket.
4 High-Risk Cash Management Traps to Avoid
Pitfall 1: Buying Treasury ETFs Without Checking State Exemption Percentages
Many investors buy ultra-short Treasury exchange-traded funds like SGOV or BIL instead of individual T-Bills.
While convenient, certain states (like California, New York, and Connecticut) enforce a strict statutory rule: a mutual fund or ETF must hold at least 50% of its assets in direct U.S. government obligations at every quarter-end for distributions to be state-tax-exempt.
If an ETF holds repurchase agreements (repos) that drop direct holdings below state thresholds, the entire dividend distribution becomes fully taxable by the state.
Pitfall 2: Mistaking Treasury Yield for Federal Tax Exemption
Do not confuse municipal bonds with Treasury Bills.
Treasury Bills are exempt from state and local taxes, but they are 100% taxable at the federal level as ordinary income.
Interest earned on T-Bills will appear on your annual IRS Form 1040 Line 2b and will be taxed according to your ordinary federal marginal bracket.
Pitfall 3: Failing to Report Box 3 on State Tax Returns
At year-end, your brokerage issues Form 1099-INT.
Treasury Bill interest is explicitly segregated into Box 3: Interest on U.S. Savings Bonds and Treasury Obligations, rather than Box 1 (ordinary bank interest).
When preparing your state tax return, verify that your tax software automatically transfers Box 3 amounts to your state subtractions/deductions schedule to ensure your state exemption is applied.
Pitfall 4: Relying on FDIC Limits for Balances Over $250,000
Bank savings accounts are protected by the Federal Deposit Insurance Corporation up to $250,000 per depositor, per institution.
Holding $500,000 in cash at a single bank exposes surplus funds to bank failure credit risk.
Treasury Bills have no dollar cap on government backing; holding $2 million in Treasury Bills carries zero principal risk because the United States government cannot default on domestic currency obligations.
Frequently Asked Questions
How do I buy Treasury Bills with zero fees?
Major discount brokerages like Fidelity, Charles Schwab, and Vanguard charge exactly $0.00 in commissions or transaction fees for Treasury auction orders.
You buy bonds at the exact auction discount price with zero markups or advisory fees.
Secondary market orders are also executed commission-free across major modern brokerage portals.
What is the minimum investment required to buy a T-Bill?
The minimum denomination for all United States Treasury Bills is $100.00.
Bonds are sold in increments of $100, meaning you can invest $100, $500, $1,000, or any multiple thereof.
This low entry threshold allows small savers to build diversified ladders alongside high-net-worth investors.
How do Treasury Bills pay interest?
T-Bills do not pay traditional semi-annual coupon checks; they are issued at a discount to par value and mature at full face value ($100).
For example, you might pay $98.70 to purchase a 13-week T-Bill at auction.
When the bond matures thirteen weeks later, the Treasury deposits the full $100.00 face value into your account: the $1.30 difference represents your earned interest.
Can I hold T-Bills inside an IRA or 401(k)?
Yes, you can purchase Treasury Bills inside Traditional IRAs, Roth IRAs, or Solo 401(k)s.
However, because IRAs are already tax-exempt, the primary benefit of state tax exemption is redundant inside retirement accounts.
T-Bills are most powerful when held in standard taxable brokerage accounts where state tax savings translate directly into higher take-home cash.
What happens if interest rates drop while I own a T-Bill?
Your yield is 100% locked in from the day of purchase through the maturity date.
If the Federal Reserve cuts interest rates next week, your existing T-Bill continues earning its higher locked-in rate until maturity.
Furthermore, falling interest rates increase the market price of existing bonds, meaning you could sell your T-Bill on the secondary market early for a slight capital gain.
The 30-Day T-Bill Cash Strategy Roadmap
- Day 1 to 5: Look up your state marginal income tax bracket and calculate your State Tax-Equivalent Yield using the STEY formula.
- Day 6 to 10: Open a taxable cash management or brokerage account at Fidelity, Charles Schwab, or Vanguard.
- Day 11 to 15: Transfer your cash reserves from your existing commercial bank HYSA into your brokerage core settlement fund.
- Day 16 to 20: Navigate to the Fixed Income trade tab, select the upcoming 4-week or 13-week Treasury auction, and submit your first non-competitive bid.
- Day 21 to 25: Enable the “Auto-Roll” feature on your active T-Bill position to automate principal reinvestment at maturity.
- Day 26 to 30: Schedule three subsequent weekly auction orders to complete your 4-tranche ladder, establishing continuous weekly liquidity.
This guide provides statutory analysis and educational instruction regarding government securities and taxation. Komon Lab does not provide formal tax preparation, banking, or registered investment advisory services. Treasury Bill yields and bank savings APYs fluctuate based on Federal Reserve monetary policy and market auction clearing dynamics. Consult a certified financial planner or tax advisor to evaluate fixed income allocations for your specific tax bracket.