She’ll Keep $250,000 in a California Bank CD. Treasury Bills Paying About the Same Are Free of State Income Tax, and the CD Will Quietly Cost Her Every Year
California taxes bank CD interest like wages, but a competing savings option sits completely outside the state's reach. A $250,000 balance turns that legal distinction into a surprisingly large annual gap that never appears on a bank statement.
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A saver renewing a $250,000 certificate of deposit at a California bank for another year faces a cost she may never see. California taxes every dollar of that CD’s interest, while Treasury bills paying about the same rate would owe the state nothing. At this balance, that gap adds up every year and never shows up as a line on her bank statement.
Treasury bills, or T-bills, are short-term loans to the federal government. They come in 4, 6, 8, 13, 17, 26, and 52-week terms. Buyers pay slightly less than face value and receive the full face value when the bill matures. That difference is the interest.
Why California Can Tax Her CD but Can’t Tax a T-Bill
Under federal law, specifically 31 U.S.C. § 3124(a), U.S. government obligations “are exempt from taxation by a State or political subdivision of a State,” and that includes the interest. The Treasury’s own summary for bills puts it simply: “Federal tax due on interest earned. No state or local taxes.”
Bank CD interest gets no such protection, so California taxes it like wages. Both kinds of interest are taxed federally, since 26 U.S.C. § 61(a)(4) lists interest as gross income. That means the federal bill is the same either way, and the whole difference comes down to state tax.
California’s most recent tax rate schedules, for 2025, charge single filers rates from 1% to 12.3%. The 9.3% rate covers taxable income between $72,724 and $371,479, where many comfortable retirees and professionals land.
What One Year of CD Interest Costs Her
On October 27, 2026, the 52-week T-bill yielded about 4.5% and the 26-week bill about 4.4%. The FDIC’s national average for a 12-month CD was 1.8% as of October 1, 2026, though that figure only covers deposits under $100,000, and the best banks pay well above it. To keep the comparison fair, this example gives her CD the same rate as the bill. The assumptions are as follows:
- She is a single filer, and her other California taxable income already puts this interest in the 9.3% bracket.
- Her one-year CD and a 52-week T-bill both pay 4.5% on $250,000.
- She takes the federal standard deduction, so state tax doesn’t reduce her federal tax.
- The money sits in a regular taxable account, so it isn’t inside an IRA.
| One year, $250,000 | Bank CD | Treasury bill |
|---|---|---|
| Interest earned | $11,200 | $11,200 |
| California tax | About $1,042 | $0 |
| Kept after state tax | About $10,158 | $11,200 |
She’d hand California roughly $1,042 a year for the same safety. Looked at the other way, her CD would have to pay about 4.9% just to break even with a 4.5% bill after state tax.
Equally Safe, Slightly More Hands-On
FDIC insurance covers $250,000 per depositor, per insured bank, for each account ownership category. At exactly $250,000, the interest she earns pushes her past that limit at a single bank under one ownership category. Treasuries are backed by the government’s full faith and credit. Both are about as safe as cash gets.
Bills take a bit more setup as she can buy them through a brokerage account or directly from the government, starting at $100, and set them to roll over automatically. If she needs the money early, she can sell a bill before it matures, though the price might be a little higher or lower depending on where rates have moved. Breaking a CD early usually means paying a penalty and giving up some interest.
Money Market Funds Can Lose the Exemption
A fund that holds Treasuries gets different state tax treatment from the bills themselves. California only lets a fund pay state-exempt dividends if at least 50% of its assets are eligible U.S. obligations at the close of each quarter (Cal. Rev. & Tax. Code § 17145(a)). Even then, only the part of the dividends that comes from that interest is exempt, under § 17145(b)(3). A pure Treasury fund can pass through most of the break. A mixed government fund that falls below the 50% line passes through none of it.
Where the State Exemption Does Nothing
Inside an IRA or any other tax-sheltered account, none of this matters. The interest isn’t taxed each year anyway, so the state exemption adds nothing. The switch only pays off when you hold money in a regular taxable account.
One Line on Last Year’s Return
First, check the interest line on last year’s California return, along with the bank’s 1099-INT and then multiply that number by her bracket rate to see what the CD actually cost her last year.
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David Beren has been a Flywheel Publishing contributor since 2022. Writing for 24/7 Wall St. since 2023, David loves to write about topics of all shapes and sizes. As a technology expert, David focuses heavily on consumer electronics brands, automobiles, and general technology. He has previously written for LifeWire, formerly About.com. As a part-time freelance writer, David’s “day job” has been working on and leading social media for multiple Fortune 100 brands. David loves the flexibility of this field and its ability to reach customers exactly where they like to spend their time. Additionally, David previously published his own blog, TmoNews.com, which reached 3 million readers in its first year. In addition to freelance and social media work, David loves to spend time with his family and children and relive the glory days of video game consoles by playing any retro game console he can get his hands on.
