For California residents, finding a safe place to park cash while earning competitive returns often comes down to three choices: high-yield savings accounts (HYSA), money market funds (MMF), or U.S. Treasury Bills (T-Bills). At first glance, HYSAs may seem attractive with their advertised APYs, easy liquidity, and FDIC insurance. However, when you account for taxes, Treasury Bills often emerge as the smarter option, especially in California, and especially as your income rises.
1. Tax Advantages for Californians
One of the biggest reasons Treasury Bills shine in California is the state tax exemption.
Treasury Bill interest is exempt from California state income tax by federal law (31 U.S.C. § 3124). This is a significant advantage that high-yield savings accounts simply cannot match. HYSA interest is fully taxable at both the federal and state levels.
For most California filers, this already tips the scales toward T-Bills. But for high-income earners, the difference becomes dramatic. Here's how the two stack up at the top federal bracket, including the 3.8% Net Investment Income Tax (NIIT) that applies to investment income above $200K AGI:
| Tax Layer | HYSA | T-Bill |
|---|---|---|
| Federal ordinary income (37%) | ✅ | ✅ |
| Net Investment Income Tax (3.8%) | ✅ | ✅ |
| California state tax (13.3%) | ✅ | ❌ |
| Combined marginal rate | 54.1% | 40.8% |
At a 4% gross yield, that gap translates to a meaningful difference in what you actually keep:
| HYSA (4% APY) | T-Bill (4% yield) | |
|---|---|---|
| Gross yield | 4.00% | 4.00% |
| After-tax yield (top bracket, CA) | ~1.85% | ~2.37% |
That's nearly 28% more after-tax income from T-Bills on the same headline rate — simply by eliminating California's 13.3% cut.
For investors not yet at the top bracket, the math is still favorable. Even at a 24% federal rate with California's middle-tier state rates, T-Bills consistently deliver higher after-tax yields than equivalent HYSA rates for California residents at virtually every income level.
2. Higher, More Predictable Returns
Treasury Bills are currently offering yields that often match or outpace the best high-yield savings accounts. With maturities ranging from 4 weeks to 52 weeks, you can lock in a rate rather than being subject to a bank's discretion.
Banks can and often do cut HYSA rates when the Fed lowers rates, sometimes with little notice. Treasury Bills, by contrast, guarantee your rate until maturity, making them a more reliable option for predictable, consistent returns.
3. Safety and Direct Government Backing
Both options are safe, but the backing differs:
- High-Yield Savings Accounts: FDIC-insured up to $250,000 per depositor, per bank.
- Treasury Bills: Backed directly by the full faith and credit of the U.S. government and is widely considered the safest asset in the world.
For investors with balances exceeding FDIC limits, a common situation for high earners, Treasury Bills offer greater security without the need to spread funds across multiple institutions.
4. Why Buy T-Bills Directly Instead of ETFs or Funds?
Some investors turn to Treasury ETFs or bond funds for convenience, but buying T-Bills directly through TreasuryDirect or a brokerage typically produces better results:
No Expense Ratios
ETFs and mutual funds charge annual fees (typically 0.05%–0.15%). Buying directly avoids this drag entirely, letting you keep more of your earnings.
No Market Price Risk
Treasury ETFs trade like stocks. Their prices fluctuate with interest rates. If you need cash before maturity, you could sell at a loss. With direct T-Bills, you hold to maturity and receive full face value.
Tax Simplicity
Direct T-Bill purchases generate straightforward federal interest income. ETFs can create distributions and additional reporting complexity at tax time.
5. Liquidity Considerations
- HYSAs offer instant access with no restrictions, a genuine advantage for emergency funds or very short-term needs.
- Treasury Bills are designed to be held to maturity, but they aren't locked up. You can sell them in the secondary market before maturity through most brokerages, though prices may fluctuate with interest rates, meaning you could receive slightly more or less than your purchase price depending on market conditions at the time of sale. For investors who want to avoid that uncertainty entirely, laddering T-Bills which is staggering maturities across 4, 12, 26, and 52 weeks ensures regular access to cash without taking on any price risk.
Bottom Line
For California residents, the math favors Treasury Bills across the board: higher after-tax returns, more predictable income, direct government backing, and no fund fees. The advantage grows sharply with income at the top bracket, the California state tax exemption alone shifts the effective tax rate from 54.1% down to 40.8%, turning a comparable gross yield into meaningfully more money in your pocket.
While HYSAs still win on pure convenience and immediate liquidity, investors looking to maximize safe, tax-efficient returns should strongly consider buying T-Bills directly particularly in a high-tax state like California where keeping more of what you earn matters as much as the rate itself.