Question: I have the opportunity to buy $10,000 worth of I-bonds this year, or $10,000 worth of TIPS in an IRA account. Which is better–or is it more or less the same risk and return? Is it better to by a TIPS bond directly, or in a bond fund?

PS: Your book was great and I enjoy hearing you on public radio. Ken, Swarthmore, PA

Answer: Thanks a lot. Just a quick definition: TIPS are Treasury Inflation Protected Securities. These inflation-indexed bonds come in 5, 10 and 20 year maturities. TIPS offer a fixed interest rate above inflation, as measured by the consumer price index. TIPS are designed to protect the value of an investment dollar against the ravages of inflation (as measured by the CPI). Uncle Sam levies income taxes on the inflation-adjusted gains before you get any of the inflation-adjusted money at maturity. That’s why you’re right to see TIPS as the better investment in a tax-sheltered account, like your IRA.

Taxes aren’t an issue with I-Bonds, a savings bond that is the federal government’s other inflation-protected security. There are no commission costs when you buy or sell savings bonds, and your savings compound tax deferred. I-bonds redeemed before the 5 year mark forfeit the 3 most recent months’ interest, but after 5 years that there is no penalty at redemption.

The key to answering this question is when do you need the money? It’s advantage I-bond if you might tap the savings at some point in the future but before retirement. You can sell the I-bonds without incurring a penalty even if you’re under 59 ½. You just pay Uncle Sam whatever you owe in taxes after the sale (and I’m assuming you’ll own them for 5 years).

In sharp contrast, if you buy TIPS in your IRA, you can’t get at that money without paying taxes on it plus a 10% early withdrawal penalty if you’re under 59 ½. You’ll have to pay a broker a fee to purchase the TIPS for you in an IRA (although the charge should be very small.) If you’re okay with the extra work and monitoring the bonds then I would lean slightly toward owning individual TIPS. This way you know what you have and when the bond will mature. You could care less about fluctuations in the bond market. But a very low cost TIPS mutual fund is just fine for those who favor its convenience.