The fixed rate of return is announced by the Treasury Department each May and November. The fixed rate of return announced in May of a given year is the same over the entire life of the I Bonds you purchase between May 1 and October 31 of that year. Likewise, the fixed rate of return announced in November of a given year applies to the entire life of I Bonds you purchase between November 1 and April 30 of the following year. The semiannual inflation rate is also announced each May and November by the Treasury Department. The semiannual inflation rate is combined with the fixed rate of an I Bond to determine the I Bond's earnings rate for the next six months.
Bonds increase in value each month, and interest is compounded semiannually.
I Bonds increase in value on the first day of the month. An I Bond's issue date is the month and year when the full issue price is received by an I Bond issuing agent. I Bonds are U.S. Treasury securities backed by the U.S. Government. I Bonds even protect you from the effects of deflation. I Bonds earn interest for up to 30 years.