Treasury Inflation-Protected Securities adjust principal up with inflation and down with deflation based on CPI changes, pay a fixed coupon every six months on that adjusted principal, guarantee repayment of whichever is greater between original and adjusted principal at maturity, come in 5-, 10-, or 30-year terms, and are available on TreasuryDirect from a $100 minimum.
How Do TIPS Use CPI Adjustments to Protect Purchasing Power?
TIPS principal rises with inflation and falls with deflation, moving in step with the Consumer Price Index (CPI) between the time of issuance and each payment date. The U.S. Department of the Treasury (TreasuryDirect) states that the principal, called par value or face value, of a TIPS goes up with inflation and down with deflationCITE:E1. The Federal Reserve Board explains that both principal and coupon payments on TIPS are adjusted for inflation as measured by the change in the CPI between issuance and the relevant paymentCITE:E5. The Federal Reserve Bank of St. Louis (FRED) describes TIPS as securities whose principal is tied to the CPICITE:E6.
What Is the Interest Payment Structure of TIPS?
TIPS pay interest twice a year at a fixed rate applied until maturity. TreasuryDirect states that TIPS pay a fixed rate of interest every six months until they matureCITE:E2. Because the coupon rate is fixed while it is applied to a principal that itself moves with the CPI, the dollar amount of each semiannual payment changes as the inflation-adjusted principal changes.
How Do TIPS Protect Principal During Deflation?
At maturity, the U.S. Treasury pays whichever is greater: the inflation-adjusted principal or the original principal, so holders cannot receive less than their initial investment even after a period of deflation. TreasuryDirect states that when a TIPS matures, the holder gets either the increased, inflation-adjusted price or the original principal, whichever is greaterCITE:E3. FRED states the same mechanism, noting that when the security matures, the U.S. Treasury pays the original or adjusted principal, whichever is greaterCITE:E7.
What Maturity Terms Does the U.S. Treasury Offer for TIPS?
The Treasury issues TIPS in three fixed terms. TreasuryDirect states that TIPS are sold for a term of 5, 10, or 30 yearsCITE:E4.
What Is the Minimum Investment to Buy TIPS on TreasuryDirect?
TreasuryDirect sets a minimum TIPS purchase of $100, in increments of $100. TreasuryDirect lists the minimum purchase for TIPS as $100CITE:E8.
TIPS Key Terms at a Glance
| Feature | Value | Source |
|---|
| Maturity terms offered | 5, 10, or 30 years | CITE:E4 |
| Interest payment frequency | Every 6 months, at a fixed rate | CITE:E2 |
| Principal adjustment | Up with inflation, down with deflation, tracking CPI | CITE:E1CITE:E5CITE:E6 |
| Repayment at maturity | Greater of adjusted or original principal | CITE:E3CITE:E7 |
| Minimum purchase on TreasuryDirect | $100, in $100 increments | CITE:E8 |
What this means: the CPI-linked principal adjustment described by TreasuryDirect and the Federal Reserve Board sets the inflation-protection mechanism, the fixed semiannual coupon described by TreasuryDirect applies that rate to the adjusted principal rather than a fixed dollar amount, and the greater-of-two-principals rule confirmed identically by TreasuryDirect and FRED caps the downside at the original investment. Structured across three maturity terms and available from a $100 minimum, these mechanisms operate together rather than independently.
Author's Take・EffectStory 編輯部
The notable structural point is that TIPS' inflation protection operates on two independent mechanisms rather than one: the CPI-linked adjustment to principal and coupon described by TreasuryDirect and the Federal Reserve Board handles the inflation side, while the greater-of-original-or-adjusted-principal rule at maturity, stated identically by TreasuryDirect and FRED, handles the deflation side. Because the fixed coupon is paid on a moving principal base rather than as a flat dollar amount, the semiannual payment amount itself becomes a running signal of how much CPI has moved since issuance across whichever of the 5-, 10-, or 30-year terms is held. Combined with a $100 minimum and $100 increments on TreasuryDirect, the structure is built for retail-scale access rather than institutional minimums. The figure worth tracking over time is how the semiannual coupon payment on a given TIPS changes relative to its original terms, since that gap is the direct, observable output of the CPI adjustment mechanism itself.