Series HH can only be bought in exchange for Series EE bonds or when you reinvest the proceeds of matured Series H bonds. Interest is periodically added to the amount you originally paid. As the interest accrues, the value of your bond increases. Interest is paid to you every six months. When you cash the bond, you receive your original investment.
Interest is added to the bond monthly and paid when the bond is cashed.
I Bonds are sold at face value, and they grow in value with inflation-indexed earnings for up to 30 years. Earnings from savings bonds are exempt from state and local taxes. Federal income taxes can be deferred until interest is received. Savings bonds can be bought at almost any bank, by mail or online. Many employers offer them through payroll deduction.