How Series I Savings Bond Interest Rates Actually Reset

Series I savings bonds have become a familiar inflation-hedging tool for retail savers, but the way their interest rate works confuses many holders. Unlike a savings account or a fixed-rate bond, an I bond's yield is not one number that stays put. It is a composite of two separate pieces that combine on a schedule tied to when you bought the bond, not to the calendar.

Two Components, One Composite Rate

Every I bond earns a composite rate built from a fixed rate and an inflation rate. The fixed rate is set by the U.S. Treasury at the time you purchase the bond and stays the same for the entire 30-year life of that bond, even if Treasury changes the fixed rate for new purchases later. The inflation rate is different: it is recalculated every six months based on changes in the non-seasonally adjusted Consumer Price Index for All Urban Consumers, or CPI-U, over the preceding six-month period. Treasury announces new fixed and inflation rates on the first business day of May and November each year.

The two pieces are blended using a formula published by Treasury: composite rate equals the fixed rate plus two times the semiannual inflation rate, plus the fixed rate multiplied by the semiannual inflation rate. Treasury guarantees that the composite rate can never fall below zero, even if the inflation component were to be sharply negative, protecting bondholders from losing principal value on the security itself.

Why Your Reset Date Is Personal, Not Universal

This is where confusion often starts. Treasury announces new rates twice a year on fixed public dates, but those announced rates do not apply to every bondholder on those same dates. Each bond earns its current composite rate for a full six-month period measured from its own issue date, not from the announcement date. If you bought a bond in March, your six-month earning periods run March-to-September and September-to-March, regardless of when Treasury makes its public announcements. Your rate resets to whatever the newly announced composite rate is only when your personal six-month cycle rolls over.

• A bond issued in January begins a new rate period every January and July.
• A bond issued in August begins a new rate period every August and February.
• The rate you lock in at each reset applies for the full six months that follow, even if Treasury changes rates again before your next reset date.

Liquidity Rules and the Early-Redemption Penalty

I bonds cannot be cashed at all during the first 12 months after purchase. Between one and five years of ownership, you can redeem the bond, but you forfeit the three most recent months of interest as a penalty. After five years, there is no penalty, and the bond continues earning interest for up to 30 years total unless you cash it sooner. This structure makes I bonds better suited to money you can set aside for at least a year, and ideally five or more, rather than as a substitute for an emergency fund with immediate access.

Purchase Limits and Tax Treatment

Treasury caps electronic purchases through TreasuryDirect at a set annual limit per Social Security number, with an additional smaller allowance available only in paper form purchased using a federal income tax refund. Interest on I bonds is exempt from state and local income tax but is subject to federal income tax. Holders can choose to report interest annually as it accrues or defer reporting it all until the bond is cashed or matures, whichever comes first. Some taxpayers may also qualify to exclude interest entirely when redemption proceeds are used to pay qualified higher education expenses, subject to income limits and other conditions set by the IRS.

The Practical Takeaway

I bonds are not a way to chase the highest headline rate at any given moment. Because the fixed-rate portion locks in for three decades at whatever level applied when you bought the bond, the timing of your purchase relative to Treasury's fixed-rate announcements can matter more over the long run than the inflation-adjusted portion, which resets regardless. Investors comparing I bonds to other cash-equivalent options such as Treasury bills, high-yield savings accounts, or short-term CDs should weigh the lockup period and redemption penalty against the inflation protection and tax deferral benefits the bonds offer.

This article is for informational and educational purposes only and does not constitute investment, tax, or financial advice. Readers should consult TreasuryDirect.gov or a qualified financial or tax professional before making decisions about savings bonds.