What an I bond is and how its rate is built
Series I savings bonds earn a combined interest rate built from two distinct elements. The first component is a fixed rate. Treasury sets this number when you buy the bond, and it remains attached to that bond for its entire lifespan. The second component is a variable semiannual inflation rate, which resets every May 1 and November 1 to reflect broader shifts in consumer prices. Because the inflation component moves up or down every six months, the total rate moves as well. A single attractive rate announcement should not be viewed as a permanent return.
Treasury calculates the total earnings using a specific composite rate formula: fixed rate plus twice the semiannual inflation rate, plus the product of the fixed rate and the semiannual inflation rate. In federal regulation at 31 CFR 359.14, this exact relationship is written as twice the sum of half the fixed rate, the semiannual inflation rate, and their product. Both versions yield the same mathematical result. When either the fixed rate or the inflation reading rises, the overall composite rate climbs. These bonds earn interest each month until you choose to redeem them or until they reach their 30-year maturity limit, whichever arrives first. Official documentation limits interest payments to that 30-year lifespan, after which the bond stops earning interest entirely.
How the inflation component responds to prices
The variable inflation adjustment is tied directly to the non-seasonally adjusted Consumer Price Index for All Urban Consumers, known as CPI-U. This index measures price changes across all items, including volatile categories such as groceries and fuel. Treasury tracks these price shifts across fixed six-month measurement windows. The November rate reset relies on price changes between March and September. The May rate reset measures price changes between September and March. The Bureau of Labor Statistics releases the final CPI-U reading roughly two weeks before Treasury publishes the updated savings bond rate.
Because the inflation rate reflects headline consumer prices, energy swings can exert a substantial effect on the outcome. For instance, in data where the twelve-month CPI-U rose 3.7 percent, gasoline prices accounted for more than half of the entire gain. Shifts in a single commodity category can alter the semiannual rate calculation, even though the index tracks hundreds of goods and services. Under deflationary conditions, Treasury applies a protective floor so that the composite rate does not drop below zero percent. Even if consumer prices drop over a six-month window, the bond will not lose principal value. Because third-party summaries sometimes truncate the official text of this deflation floor, reviewing the details directly on the primary TreasuryDirect rate tables is a prudent step.
The November 2026 rate in context
For Series I bonds issued from November 1, 2026 through April 30, 2027, the published composite rate is 5.51 percent. This total combines a 1.40 percent fixed rate with a 2.04 percent semiannual inflation rate. On an annualized basis, that 2.04 percent semiannual figure represents roughly 4.08 percent. The 1.40 percent fixed component marks the highest base rate offered on new Series I savings bonds since November 2006. The 5.51 percent composite rate is also the highest total initial yield on newly issued bonds since November 2022, when headline composite yields reached 6.89 percent.
The preceding period, which covered May 1 through October 31, 2026, carried a composite rate of 4.26 percent. That earlier yield was derived from a 0.90 percent fixed rate and a 1.67 percent semiannual inflation adjustment. Looking at the two periods side by side shows how both parts contribute to the final payout. The fixed rate climbed by 50 basis points, and the inflation rate jumped as well. For a saver holding an older bond, the composite rate does not adjust on November 1 automatically. Instead, each individual bond adopts the new variable inflation component at its own six-month anniversary based on its original purchase month, as tracked by independent inflation tracking analyses. Two bonds purchased in different months will earn different rates during the same calendar stretch.
Holding periods, penalties, and what the rate does not promise
Series I bonds come with strict timing rules that buyers must understand before committing funds. Federal rules enforce a mandatory 12-month minimum holding period during which you cannot redeem the bond under any condition. If you cash in the bond after 12 months but before five full years have passed, you forfeit the previous three months of accrued interest. For a $10,000 bond earning an annualized 5.51 percent, the first six months of interest totals about $276. Because of the initial one-year lockup and the early redemption penalty, these bonds are not an appropriate repository for emergency cash.
A headline composite rate is only guaranteed for six months. A 5.51 percent rate does not mean you will earn 5.51 percent over a full year or across the full 30-year life of the bond. Once your bond completes its initial six-month cycle, its yield resets to match the semiannual inflation component that Treasury announces next, while keeping its original 1.40 percent fixed rate. Marketing descriptions that claim savings bonds offer guaranteed shields against inflation often gloss over this reset mechanic. The variable portion adjusts downward whenever inflation cools, which means your actual annual return fluctuates constantly.
Comparing an existing bond with a new one
Savers who hold bonds from prior years often evaluate whether to redeem an existing asset to capture the 1.40 percent fixed rate on a new purchase. Evaluating that decision requires comparing the fixed component on your existing bond against the current fixed rate, rather than comparing only the headline composite numbers. When you redeem an existing bond that is under five years old, you pay an exit cost equal to three months of interest. You must hold the replacement bond long enough for the difference in fixed rates to recover that forfeited interest.
Third-party research published by savings bond tracking specialists illustrates how long that recovery can take. If you replace an older bond carrying a 0.90 percent fixed rate with a 1.40 percent bond, closing that 0.50 percent gap takes roughly 29 months of holding the new bond. For a bond carrying a 1.20 percent fixed rate, recovering the lost interest penalty against a 0.20 percent gap takes approximately 6.3 years. For a bond with a 1.30 percent fixed rate, making up the penalty against a narrow 0.10 percent difference can require roughly 13.5 years. These estimates assume constant interest conditions, so actual recovery timelines will vary.
Before deciding to switch assets, check the following details:
- The exact fixed rate stamped on your current bond, which never changes.
- The calendar month when your current bond enters its next semiannual rate reset.
- The total months of interest penalty you will sacrifice if the bond is under five years old.
- The time required for the fixed rate differential to offset that forfeited penalty.
Public rate summaries rarely cover the nuanced tax implications of Series I bonds, such as federal tax deferral rules or exemptions from state and local income taxes. They also omit annual purchase limitations, which cap electronic purchases at $10,000 per Social Security number per calendar year. Savers evaluating how these assets fit into their broader financial life should review the primary documentation on federal portals and speak with a certified tax professional.
