Definition
A U.S. savings bond whose rate combines a fixed rate and an inflation rate that resets every six months; the limit is $10,000 a year in electronic bonds.
What it means
Series I savings bonds are sold by the Treasury through TreasuryDirect. Their rate has two parts: a fixed rate that lasts for the life of the bond and an inflation rate based on the Consumer Price Index that changes every May 1 and November 1. For bonds bought from May through October 2026, the combined rate is 4.26%, including a fixed rate of 0.90%. Each person can buy up to $10,000 in electronic I bonds per calendar year. You must hold an I bond for at least one year, and if you cash it before five years you lose the last three months of interest. Interest is exempt from state and local tax, and federal tax can be deferred until you cash the bond or it stops earning interest after 30 years.
Example
A $5,000 I bond bought in June 2026 earns at a 4.26% annual rate for its first six months, about $107 for that period, and then a new rate that depends on inflation.
Illustrative numbers only. Your situation will differ.