The Treasury Department determines interest rates for both Series EE and Series I savings bonds, which may fluctuate every six months. As of May 2023 through October 2023 issuance period, Series EE savings bonds have been set to earn a fixed annual interest rate of 2.50%. Series I savings bonds, on the other hand, are accruing a composite rate of 4.30% during the same period. This rate comprises a fixed component and an additional part indexed to inflation, which is adjusted semi-annually.