By Kevin Luu, Co-Founder and Chief Learning Officer. Reviewed on 2026-09-30.
There is no special HYSA tax rate. Interest from a high-yield savings account is taxed as ordinary income, at the same marginal rate as your next dollar of salary. For a California household earning $750,000 to $3 million, that usually means 35% or 37% federal, plus the 3.8% Net Investment Income Tax, plus 9.3% to 13.3% California tax, so roughly 48% to 54% of every interest dollar goes to tax.
A Washington family at the same income pays the federal part (about 39% to 41%: 35% or 37% plus 3.8%) and no state tax on interest for 2026. The practical question for both is not “how much is my HYSA taxed” but “after tax, is this the right place for this much cash?”
How HYSA interest is taxed for a high-income family in 2026
Three layers can apply to the same interest dollar:
- Federal income tax. Interest is ordinary income. For 2026 the federal rates are 10% to 37%. A married couple filing jointly reaches the 35% bracket above $512,450 of taxable income and the 37% bracket above $768,700 (IRS Rev. Proc. 2025-32).
- Net Investment Income Tax (NIIT). An extra 3.8% on investment income, including interest, once modified AGI is above $250,000 for joint filers ($200,000 single). That threshold is not indexed, so almost every household in our range pays it on every dollar of interest (IRS, NIIT).
- State income tax. California taxes interest as ordinary income. The latest published brackets (2025) put joint filers at 9.3% up to $742,958 of taxable income, 10.3% to $891,542, 11.3% to $1,485,906, and 12.3% above that, plus a 1% Behavioral Health Services Tax on taxable income over $1,000,000 (FTB 2025 rate schedules). California’s 2026 schedules were not yet published at review. Washington has no individual income tax in 2026 (WA DOR), and its capital gains tax does not reach bank interest.
Two things do not apply. Interest is not wages, so there is no Social Security, Medicare or California SDI on it. And the state tax gives almost no federal offset: for joint filers with modified AGI above about $606,333, the 2026 SALT deduction cap phases down to $10,000, which most of these families already fill with property tax and wage withholding.
Worked example: $250,000 of cash in a California household earning $1.2 million
Assumptions (illustrative): married, two W-2 earners with salary, bonus and RSUs totaling $1.2 million; taxable income about $1.15 million for both federal and California; $250,000 held in a high-yield savings account at an assumed 4.00% APY all year. Rates change often; plug in your own.
| Layer | Marginal rate on interest | Tax on $10,000 of interest |
|---|---|---|
| Federal (37% bracket, 2026) | 37.0% | $3,700 |
| NIIT | 3.8% | $380 |
| California (11.3% bracket + 1% over $1M, 2025 schedule) | 12.3% | $1,230 |
| Total | 53.1% | $5,310 |
The account pays $10,000. The family keeps $4,690. The 4.00% headline rate is about a 1.88% after-tax yield.
The same family in Washington would owe $4,080 (37% plus 3.8%) and keep $5,920, a 2.37% after-tax yield. A household near the bottom of our range, say $750,000 of income in California with about $700,000 of taxable income, sits in the 35% federal and 9.3% California brackets: 35% + 3.8% + 9.3% = 48.1% on interest.
The California comparison that matters: HYSA vs Treasury bills
Interest on U.S. Treasury bills, notes and bonds is subject to federal income tax but exempt from all state and local income taxes (IRS Topic 403; TreasuryDirect). NIIT still applies. For a California family in a high bracket, that state exemption is worth more than a small difference in posted rates.
| $250,000 for one year, CA household above | HYSA at 4.00% (assumed) | T-bills at 4.00% (assumed) |
|---|---|---|
| Interest | $10,000 | $10,000 |
| Tax rate | 53.1% | 40.8% (no CA tax) |
| Tax | $5,310 | $4,080 |
| Kept | $4,690 | $5,920 |
At equal yields the Treasury route keeps $1,230 more per year on $250,000. Put another way, for this family a 4.00% T-bill matches an HYSA paying about 5.05% (4.00% x 59.2% / 46.9%). Few savings accounts close that gap.
A Treasury money market fund can pass through part of the state exemption, but California applies its own conditions to fund dividends, so check the fund’s annual state tax information before counting on it. In Washington the exemption does nothing in 2026, so the choice comes down to rate, access and convenience.
The trade-offs are real. A savings account moves money in a day and is FDIC-insured to the standard limits. T-bills mature on a schedule and their price can move a little if sold early. Many families keep one to two months of spending in savings and the rest of the reserve in a Treasury ladder or fund.
Why this family often holds more cash than it needs, and how RSUs cause it
The biggest cash balance in many tech and biotech households is not the emergency fund. It is money set aside for a tax bill. Employers usually withhold federal tax on RSU vests and bonuses at the 22% supplemental rate (37% only on supplemental wages over $1 million in a year) (IRS Pub 15, 2026). A family in the 37% bracket owes more than that.
Example: $400,000 of RSUs vest during the year. Federal withholding at 22% is $88,000; the federal tax at 37% is $148,000. That leaves a $60,000 federal shortfall before California, which many families park in an HYSA until April. In California those balances can be worth holding in a state-tax-free vehicle, and worth sizing correctly so they do not sit idle for years. See how we handle this under tax management.
Interest also counts toward your estimated tax. Wage withholding is set from your W-4 and does not see interest income. The IRS safe harbors are based on current- or prior-year tax, and higher-income taxpayers face stricter prior-year rules (IRS Topic 306). Large interest plus under-withheld RSUs is a common way to land an underpayment penalty.
Form 1099-INT: what you will receive and what you must report
Banks send Form 1099-INT when they pay you $10 or more of interest in a year. You must report all taxable interest on your return even if no 1099-INT arrives (IRS Topic 403). Interest is taxable in the year it is credited to your account, not when you withdraw it. Families with accounts at several online banks should list them for their preparer each January, because small 1099s are easy to miss.
Savings in your child’s name: the kiddie tax
Grandparents often want to open a savings account for a young child. Interest in the child’s name (including a UTMA account) is the child’s income, but the kiddie tax limits the benefit. For 2026, the first $1,350 of a child’s unearned income is tax-free, the next $1,350 is taxed at the child’s rate, and anything above $2,700 is taxed at the parents’ rate (Rev. Proc. 2025-32; Form 8615 instructions).
Example: $100,000 of gifts held in cash for a six-year-old at an assumed 4.00% earns $4,000. The first $2,700 is taxed lightly; the remaining $1,300 is taxed at the parents’ 37% federal rate, plus any state tax. More important, cash earmarked for a child who is 12 years from college is usually in the wrong account. Our guide to UTMA withdrawal tax rules covers what happens when that money is spent or transferred. For money that will be invested rather than held, see how a taxable brokerage account is taxed.
Common mistakes we see
- Comparing headline APYs without comparing after-tax yields. In California, a state-exempt Treasury at a lower rate can beat a higher-rate savings account.
- Holding a year or more of RSU tax reserve, or several years of spending, in savings by default.
- Forgetting NIIT. Once modified AGI is above the $250,000 joint threshold, it adds 3.8% to interest income.
- Assuming Washington stays tax-free. Washington enacted a 9.9% income tax on AGI over $1,000,000 starting January 1, 2028 (WA DOR). How it will treat interest is pending state guidance, so revisit cash placement before 2028.
What to write down for your kids
Most families never record why they hold the cash they hold. A one-page note can do it: how many months of spending you keep liquid, where the tax reserve sits and why, and what rate difference would make you move it. Ten years from now your children will see the balances, not the reasoning, unless you write it down. As Kevin Luu puts it: “Your kids don’t need to inherit your portfolio. They need to inherit your decision-making process.” Our family governance work keeps notes like this in one place.
FAQ
Is HYSA interest taxed as capital gains?
No. Interest is ordinary income at both the federal and state level. Long-term capital gains rates (0%, 15%, 20% federal) never apply to savings interest. California taxes both interest and capital gains as ordinary income anyway, but federally the distinction matters: interest is taxed at up to 37%, plus 3.8% NIIT.
Do I pay tax on HYSA interest if I don’t withdraw it?
Yes. Interest is taxable in the year it is credited to your account, whether or not you move it out. Leaving it to compound does not defer the tax. Only interest inside a tax-advantaged account, such as an IRA or HSA, is sheltered until withdrawal.
Is CD or money market interest taxed differently?
No. Interest on bank accounts, money market accounts and certificates of deposit is taxable interest under the same rules (IRS Topic 403). What changes the result is the issuer: U.S. Treasury interest is exempt from state tax, and some state and municipal bond interest is exempt from federal tax.
Next step
Add up the cash you hold across every bank today and label each balance: spending, emergency, tax reserve or “no reason.” The last two are where a California family usually finds after-tax yield. If you want a second set of eyes, the Tax & Wealth Assessment from Age Five Family Office™ covers cash placement alongside RSUs and withholding.
This is general education, not individual tax advice. The right move depends on your family’s full picture.
Kevin has advised high-income W-2 tech and biotech families since 2015, and leads the education-first Age Five Family Office from Brea, California.
Connect on LinkedIn → · About KevinThis is part of how we approach Investment & Risk Management for high-income W-2 families at Bright Advisers.
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