CFR › Title 31 › Part 359 › §359.1631 CFR §359.16Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗Copy link(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.