If you live in a high-tax state, there is a perfectly legal tax advantage hiding in plain sight that most savers overlook: U.S. Treasury bills. While every dollar of HYSA interest is taxed at both the federal and state level, T-bill interest escapes state and local income tax entirely. For residents of California, New York, or similar states, this difference can be worth hundreds of dollars a year on the same cash balance.
What Are T-Bills and How Do They Work?
Treasury bills are short-term debt instruments issued by the U.S. government, with maturities ranging from 4 weeks to 52 weeks. You buy them at a discount and receive the full face value at maturity; the difference is your return. They are backed by the full faith and credit of the U.S. Treasury — considered effectively risk-free. Unlike FDIC insurance (which covers up to $250,000 per bank), there is no cap on T-bill safety.
- Liquidity: Can be sold on the secondary market through any major brokerage.
- Minimum purchase: $100 via TreasuryDirect.gov or a brokerage.
- Tax treatment: Federally taxable as ordinary income; exempt from all state and local income taxes.
The Math in Action
Suppose both a T-bill and an HYSA pay exactly 5.0% APY, and you have a $50,000 balance. You are a California resident in the 24% federal bracket facing a 9.3% state rate.
Same headline rate. But the T-bill delivers $230 more per year on your $50,000 purely by eliminating the state tax layer.
T-Bills vs. HYSAs: Side-by-Side Comparison
| Feature | HYSA | T-Bills |
|---|---|---|
| Federal Tax | Fully taxable (ordinary income) | Fully taxable (ordinary income) |
| State & Local Tax | Fully taxable | 100% Exempt |
| Safety | FDIC insured up to $250k | U.S. Treasury backed (no cap) |
| Liquidity | Instant withdrawal | Sellable via brokerage; not instant |
| Rate Type | Variable (changes anytime) | Fixed at purchase for the term |
| Best For | Emergency fund, everyday savings | Medium-term cash in high-tax states |
Who Benefits Most (and Least)
The state exemption is most powerful for residents of California, New York, New Jersey, Oregon, and Minnesota — states where marginal rates can exceed 9–13%. Residents of no-income-tax states like Florida, Texas, or Nevada get zero benefit from this specific exemption (they were already paying no state tax on HYSA interest), so T-bills win only if their rate is higher in those cases.
Not sure if T-bills beat your HYSA after tax? Enter your state rate and federal bracket into the Tax Drag Calculator to compare your real net yield across both options instantly.
This is educational content, not investment or tax advice. Consider your specific situation and consult a financial or tax professional before moving funds.
Calculate Your Savings After-Tax Yield
Taxes can quietly cut your advertised high-yield savings interest rate by 30% or more. Use our interactive calculator to find your combined marginal bracket, see your true net yield, and visualize your real compounding growth.