Yup, after 30 years there is no more interest and a tax bill, whether you cash them or not. Back before computers, my parents bought a bunch of bonds during WWII and put them in a drawer. They all hit the 40 year mark (an extra 10 years was added for the WWII bonds) in the mid-80s but no tax bill was received as they had never been entered in a database. I did pester my parents to cash them in and then pay the taxes, but they decided to roll them over to HH bonds to defer the taxes even further (HHs pay current income, which is taxable). You can't do that anymore, but it was a useful tool. Still have some of those left (not from the WWII bonds, but later issues - HHs are only good for 20 years), but the interest rate resets every 10 years and it's currently 1.5%.