Key takeaways
- The 4.26% on new I bonds (May–October 2026 issue dates) is a six-month composite rate from Treasury, not a bank APY.
- A high-yield savings APY can move whenever the bank decides. I-bond rates lock for six-month slices, then reset from CPI-U plus a fixed rate that never changes on that bond.
- You cannot treat I bonds like a checking overflow. There is a one-year lock, a purchase cap, and a three-month interest penalty if you cash out before five years.
Search boxes are full of “I bond rate” again because Treasury posted a new composite on May 1. For bonds issued from May 1, 2026 through October 31, 2026, that number is 4.26%. People paste it next to a 4.00% high-yield savings tile and call it a winner. That comparison is sloppy. One figure is a Treasury formula for a six-month earning period. The other is a marketing APY on a deposit product the bank can reprice.
If you only remember one distinction: APY is a bank promise that can be edited. The I-bond composite is a published rate for a defined window on a specific bond.
What 4.26% actually is
Series I savings bonds pay a composite rate built from two pieces. The fixed rate is set when you buy and stays for the 30-year life of that bond. For this issue window it is 0.90%. The inflation rate is tied to the Consumer Price Index for All Urban Consumers (CPI-U) and is announced twice a year, in May and November.
Treasury’s own arithmetic for this window:
Fixed 0.90% plus twice the 1.67% semiannual inflation figure, plus a small cross term, then rounded. That is how you get 4.26%. The 1.67% came from CPI-U moving from 324.8 in September 2025 to 330.213 in March 2026. None of that is a bank’s teaser.
The 4.26% applies for the first six months after issue on a new bond bought in this window. It is an annualized rate for that slice. It is not “you will earn 4.26% every year until 2056.”
Read the source, not a screenshot: I bonds interest rates on TreasuryDirect and the May 1, 2026 Fiscal Service release.
Your old I bonds are not on “the” rate
Headlines say “the I bond rate.” Owners bought in different months, so they sit on different clocks. Treasury announces new inflation components in May and November. Your bond’s six-month earning period is dated from your issue month. A July purchase does not jump to the May table on May 1. It waits until its own six-month mark.
The fixed rate also differs by purchase window. A bond you bought in 2022 still has whatever fixed rate was printed then. That is why two people arguing in a comments section can both be right about “their” rate and still be talking past each other.
What a high-yield savings APY is doing
A high-yield savings account is a bank (or credit union) deposit. The APY is an annualized yield that assumes the advertised rate stays put and interest compounds as disclosed. Banks cut and raise those rates as funding needs change. They do not wait for a Treasury calendar.
Short-term bank yields still live in the neighborhood of Fed policy. The FOMC has held the federal funds target range at 3.5% to 3.75% through the July 29, 2026 meeting. That range is overnight money between banks. It is not your savings APY, and it is not a mortgage coupon. We already walked through that lag here: what the federal funds rate actually changes.
When people say “savings should be 4% because the Fed is at 3.75%,” they are mixing a policy range with a retail product. Some HYSA tiles are above the funds rate. Some have already drifted under it. Shop the APY on the day you care, then assume it can move next week.
Deposits at FDIC-insured banks are insured up to the standard limit when structured correctly. That is a different backstop than a Treasury security. The FDIC’s deposit insurance explainer is the boring page worth a bookmark. Credit unions have NCUA coverage with its own rules.
Liquidity is the real fork
You can usually pull HYSA cash in a day or two. That is the product. I bonds are not that.
- You cannot redeem an I bond in the first 12 months.
- If you redeem before five years, you forfeit the last three months of interest.
- Electronic I bonds are bought in TreasuryDirect. Paper I bonds are no longer a walk-in product; leftover paper paths are narrow (tax-refund paper still exists under Treasury’s current rules, with a separate cap).
- The standard electronic purchase limit is $10,000 per Social Security number per calendar year. That cap is why I bonds cannot swallow a home-sale parking lot the way a savings account can.
If the money might become a roof repair in eight months, the one-year lock is not a footnote. It is a veto.
Tax is the other fork
I-bond interest is subject to federal income tax. It is exempt from state and local income tax. You can defer reporting the interest until you redeem or the bond finishes its 30 years, which is why people like them in taxable accounts. There is also an education tax exclusion with income limits and timing rules. Those live in IRS publications, not in a rate tweet. Start with IRS Topic 403 (interest received) and the savings-bond education section in Publication 970.
HYSA interest is ordinary income at the federal level and typically at the state level. You get a 1099-INT. No special inflation formula. No 30-year clock.
A fair comparison, not a scoreboard
Put $10,000 in a HYSA at 4.00% APY. If the bank holds that rate for a year and compounds as advertised, you are in the ballpark of $400 before tax. If they drop the APY to 3.20% in month four, you do not get a hearing at Treasury.
Put $10,000 into new I bonds in August 2026. You get 4.26% annualized for the first six-month slice on that issue window’s terms. The next slice depends on the November inflation announcement and your issue month. You cannot touch it for a year. You are capped at the annual limit. You have a Treasury claim, not a bank login.
Neither sentence says “buy this.” It says the units are different. Rate shopping without the lock, the cap, and the tax treatment is how people lose six months of optionality for 20 basis points of bragging.
When the I bond is the better tool
You have cash you will not need for at least a year. You already used (or do not want) bank deposits for the emergency slice. You care about inflation adjustment more than same-day liquidity. You want state-tax-exempt interest and you will actually open a TreasuryDirect account instead of screenshotting a rate.
The 0.90% fixed rate is the part that lasts. If future inflation prints are low, the composite sags. If inflation runs hot again, the inflation component does the lifting. That is the design. It is not a CD.
When the HYSA is the better tool
The money is an emergency fund, a tax payment, or a down payment with a date. You might need it inside twelve months. You already hit the $10,000 I-bond cap. You do not want another login. You would rather accept a moving APY than a statutory lock.
A money market fund or T-bills are a third family. They are not HYSA. They are not I bonds. Mixing all three into one “cash” bucket is how statements get weird.
How to buy without folklore
Open or use a TreasuryDirect account at Treasury’s I bond page. Buy Series I, electronic. Name the owner correctly the first time; registration mistakes are a pain. Buy only what you can leave alone for a year.
For the savings side, compare APY, minimums, and whether the bank is actually FDIC-insured. Screenshot the APY. Banks change landing pages. The 1099 will not care what the banner said in March.
Next rate drop from Treasury is the November 2026 announcement, for bonds issued November 1, 2026 through April 30, 2027. If you are buying before Halloween 2026, you are still in the 4.26% first-slice window for new issues. After that, use the new table. Do not memorize this post.
Educational only. Not tax, legal, or investment advice. Limits, inflation components, and bank APYs change. TreasuryDirect and the IRS control the rules; a blog post does not.
