31 CFR § 359.16
When does interest accrue on Series I savings bonds?
July 31, 2023
§ 359.16 When does interest accrue on Series I savings bonds?
(a) Interest, if any, accrues on the first day of each month; that is, we add the interest earned on a bond during any given month to its value at the beginning of the following month.
(b) The accrued interest compounds semiannually.