I Bonds: The Inflation-Protected Savings Tool From the U.S. Treasury

Series I savings bonds are a U.S. Treasury-issued savings instrument that earns a composite interest rate: a fixed rate set at purchase plus an inflation adjustment tied to the Consumer Price Index that resets every six months in May and November. When inflation runs high, the rate is high. When inflation drops, so does the rate — but it can never go negative, meaning the bond can't lose purchasing power even in deflationary conditions. That floor is one of the most valuable features of any savings instrument.

During the 2021 to 2022 inflation surge, I bonds briefly paid composite rates above 9%, drawing widespread attention from investors who had previously ignored them. The product was never intended as an investment vehicle — it's a savings product with a $10,000 annual purchase limit per Social Security number. That ceiling is real and constraining for anyone looking to move large sums, but for an emergency fund, a short-term savings goal, or a meaningful allocation, I bonds are worth understanding.

How the composite rate is calculated

The composite rate formula is: fixed rate + (2 × semiannual inflation rate) + (fixed rate × semiannual inflation rate). The fixed rate is set when you buy and stays with that bond for its 30-year life. The inflation component resets twice a year based on the CPI-U (urban consumers) measured in March and September. If you buy in November, your first six months earn the rate set that November, then it adjusts the following May — regardless of when you bought. Understanding the reset schedule helps you time purchases to capture favorable rates.

The fixed rate component has historically been close to zero during low-rate environments — it was 0% for most of 2020 to 2022. In late 2023 and into 2024, the fixed rate moved to 1.3%, which is meaningfully better: a 1.3% fixed rate means you'll always earn at least 1.3% above inflation for the life of that bond. Bonds purchased when the fixed rate is higher are more valuable long-term, since the fixed portion compounds on top of whatever inflation rate prevails each period.

Purchase limits, holding rules, and penalties

Electronic I bonds are purchased exclusively through TreasuryDirect.gov (no brokerage access), with a $10,000 limit per person per calendar year. An additional $5,000 can be purchased annually using a federal tax refund in paper form — meaning a household filing jointly could theoretically buy $25,000 in a single year if they direct their refund appropriately. Bonds must be held at least 12 months; redeeming before five years costs you the three most recent months of interest. After five years, redemption is penalty-free.

Interest accrues but isn't paid out until redemption — you don't receive periodic interest payments. This deferred taxation is a feature: you can choose when to recognize the income by choosing when to redeem. Federal income tax is owed at redemption (or maturity at 30 years); I bonds are exempt from state and local income taxes. If you use I bonds to pay for qualified higher education expenses, the interest may be fully or partially excluded from federal income tax, subject to income limits.

I bonds vs. high-yield savings accounts — the honest comparison

High-yield savings accounts (HYSAs) offer instant liquidity, no purchase limits, and rates that tracked the federal funds rate closely from 2022 to 2024 — reaching 5% to 5.5% during peak tightening. I bonds during the same period paid similar or higher rates but with a 12-month lockup. When the Fed starts cutting rates, HYSA yields fall almost immediately. I bond rates lag by up to six months due to the reset schedule, which briefly made them more attractive in a falling-rate environment. The correct framing: I bonds suit money you won't need for at least a year; HYSAs suit the liquidity reserve.

The strongest argument for I bonds is the structural guarantee: no other retail savings product directly tracks CPI inflation with a zero-floor guarantee, government backing, and state tax exemption simultaneously. Treasury Inflation-Protected Securities (TIPS) do something similar but trade at market prices, meaning they can lose nominal value in rising-rate environments. I bonds don't — they're savings bonds, not tradable securities, so market price risk doesn't apply. For a portion of a savings strategy specifically dedicated to preserving purchasing power, no equivalent product exists.