TIPS or I Bonds? A Decision Guide Built Around the Constraints

By Swoopr Editorial Team Published 2026-09-17 Research-assisted analysis. Verify sources before acting.

Key Takeaways

• I Bonds are purchase-limited to $10,000 per person per year ($5,000 more via tax refund); TIPS have no purchase limit and can be bought in any quantity on the secondary market.
• I Bonds cannot be redeemed in the first 12 months; TIPS can be sold any business day, though at market price which may be below par.
• I Bonds carry no duration/price risk; TIPS carry price risk because their market price adjusts with real interest rates (duration risk).
• I Bond interest is deferred for federal tax purposes until redemption; TIPS inflation adjustments are taxed as ordinary income in the year accrued, creating phantom income in taxable accounts.
• For amounts above $10,000, TIPS or a TIPS fund is the only option; for small allocations with long time horizons, I Bonds often provide better after-tax real returns.

How Each Instrument Provides Inflation Protection

TIPS adjust both their principal and coupon payments for changes in the Consumer Price Index (CPI). When CPI rises, the principal increases, and the coupon (a fixed percentage of principal) rises proportionally. At maturity, the holder receives the greater of the adjusted principal or par value, protecting against deflation as well. I Bonds adjust their composite yield using two components: a fixed rate set at issuance (which stays constant for the bond's 30-year life) and a variable rate based on CPI-U that resets every six months in May and November. The composite yield cannot go below 0%, so I Bonds never lose nominal value.

The Liquidity Constraint Drives Most Decisions

The 1-year lock-up on I Bonds is a hard constraint: money committed to I Bonds is unavailable for emergencies during the first year, full stop. The early redemption penalty (forfeiture of 3 months of interest for redemptions in months 12 through 60) reduces but does not eliminate I Bond returns in the near term. TIPS held directly can be sold any business day; a TIPS fund provides daily liquidity at NAV. For an emergency reserve or funds needed within 12 to 24 months, TIPS or short-term TIPS funds dominate. For capital that is genuinely available for 12+ months, I Bonds become competitive.

Tax Treatment Creates a Meaningful Difference in Taxable Accounts

I Bond interest accrues tax-deferred; the investor owes federal income tax only when the bond is redeemed (state and local tax exempt). This deferral compounds the real after-tax return. TIPS inflation adjustments to principal are treated as ordinary income in the year accrued, even though the investor has not received cash. In a year when inflation runs at 6%, a $10,000 TIPS position generates approximately $600 in taxable phantom income. In tax-deferred accounts (IRA, 401k), the phantom income problem disappears; TIPS become fully competitive with I Bonds in those accounts.

Decision Framework

Use this logic: If the investment amount is above $10,000, you cannot use I Bonds for the full amount and must use TIPS for the excess. If the account is tax-deferred (IRA, 401k), TIPS and TIPS funds have no phantom-income disadvantage; use whichever is more convenient to hold. If the account is taxable and the amount is within the $10,000 limit, I Bonds are typically preferred for the first 5 years due to tax deferral and lack of price risk. If you may need the funds within 12 months, I Bonds are unavailable; use a short-term TIPS ETF or keep funds in a high-yield savings account. If you want to lock in a specific real yield for a defined maturity, individual TIPS bought at auction offer this precision.