EE bonds replaced the Series E Bonds. They are purchased at a discount of half their face value in $50 to $10,000 denominations, but you cannot buy more than $30,000 (face value) during any calendar year. EE bonds increase in value as the interest accrues or accumulates and pay interest for 30 years. When EE bonds "mature," or come due, you are paid your original investment plus all of the interest.
