TIPS: Treasury Inflation-Protected Securities Explained

Key Takeaways

• TIPS principal adjusts with CPI-U; coupons are computed on the adjusted balance, so both grow with inflation.
• Break-even inflation equals the nominal Treasury yield minus the TIPS yield at the same maturity.
• Phantom income from annual principal accrual is taxable each year, making TIPS most efficient in tax-deferred accounts.
• TIPS still carry real-rate risk; rising real yields push TIPS prices lower regardless of the inflation environment.

What It Is

A TIPS is a marketable Treasury bond with inflation-linked principal. At auction, the Treasury sets a fixed real coupon rate. Every six months the principal is revalued using the ratio of the current reference CPI-U to the CPI-U at issue, and the semiannual coupon is calculated on the adjusted principal. At maturity, the holder receives the greater of the inflation-adjusted principal or the original face value. That second clause is the deflation floor: even if the price level falls over the bond's life, you get your original principal back.

TIPS currently come in 5-year, 10-year, and 30-year maturities and are auctioned on a regular schedule published by TreasuryDirect.

The Intuition

Nominal Treasuries pay a fixed number of dollars on fixed dates, regardless of what those dollars can buy later. If inflation runs hotter than the market expected when the bond was issued, the real value of those dollars shrinks. TIPS fix that by indexing the payoff to the CPI.

Investors use TIPS to lock in a known real return. A 10-year TIPS with a 1.5 percent real yield promises 1.5 percent per year above whatever CPI-U turns out to be, over a decade. A 10-year nominal Treasury promises a fixed total rate and leaves you exposed to the inflation outcome.

The gap between the two tells you what the market expects for inflation.

Break-even Inflation = Nominal Yield - TIPS Yield (same maturity)

If the 10-year nominal is at 4.3 percent and the 10-year TIPS is at 1.8 percent, the implied break-even inflation is 2.5 percent. An investor who thinks actual inflation will beat 2.5 percent over the next decade prefers TIPS. Someone who thinks it will undershoot prefers nominals.

How It Works

The mechanics hinge on the index ratio, published daily by the Treasury.

Index Ratio (t) = Reference CPI-U (t) / Reference CPI-U (at issue)
Adjusted Principal (t) = Original Principal x Index Ratio (t)
Semiannual Coupon (t) = Adjusted Principal (t) x (Real Coupon Rate / 2)

The reference CPI-U uses a two-month lag: the CPI figure for any given day is interpolated from the CPI releases for two and three months earlier. That lag means there is a small, mechanical tracking error against current inflation.

Tax treatment is a key quirk. The annual increase in adjusted principal is taxable as ordinary income in the year it accrues, even though the holder does not receive that cash until maturity. This is often called phantom income. For that reason, TIPS are typically held inside tax-deferred accounts where the accrual is not taxed each year.

The deflation floor only applies to the original principal at maturity. Semiannual coupons can still shrink during a deflationary stretch because they are computed on the adjusted (smaller) principal.

Worked Example

A 10-year TIPS is auctioned at a real yield of 2.0 percent and a real coupon rate of 2.0 percent. You buy $10,000 face value at par.

Five years in, cumulative CPI inflation has been 12 percent. The index ratio is 1.12. Your adjusted principal is $11,200. The next semiannual coupon is:

Coupon = $11,200 x 0.02 / 2 = $112

Compare that with the original coupon of $10,000 x 0.02 / 2 = $100. The dollar coupon has grown because the principal has.

Fast forward to maturity. Suppose cumulative CPI growth over the full 10 years is 25 percent. Final principal returned is $10,000 x 1.25 = $12,500. In a deflationary alternate timeline where cumulative CPI fell 5 percent, the deflation floor kicks in and you still get your original $10,000 back at maturity, though coupons along the way would have been computed on a principal below par.

Common Mistakes

1. Comparing TIPS yields directly with nominal yields. A 1.8 percent TIPS yield is not worse than a 4.3 percent nominal yield. They measure different things. Use the break-even to compare, and decide whether your personal inflation forecast is higher or lower than the market's implied rate.

2. Holding TIPS in a taxable account. Phantom income can create a cash-flow gap between the tax bill and the coupon received. TIPS usually work better inside an IRA, 401(k), or other tax-deferred account.

3. Assuming TIPS have no duration risk. Real yields move. If real rates rise, TIPS prices fall, just like any other bond. The 2022 experience, when long-dated TIPS posted large negative returns despite high inflation, is the classic reminder.

4. Overweighting the deflation floor. The floor only guarantees the original principal at maturity, not interim prices. You can still lose money in a TIPS if real rates spike or if deflation drives coupons below expectations.

5. Forgetting the reference CPI lag. TIPS track inflation with a two-month delay embedded in the reference CPI. In fast-moving inflation regimes, that lag matters for short-horizon comparisons.

Frequently Asked Questions

What happens to TIPS if inflation turns negative? If cumulative inflation over the bond's life turns negative, the adjusted principal falls below the original face value. Coupons paid along the way are smaller because they are computed on the deflated principal. However, at maturity the deflation floor guarantees the holder receives at least the original par amount, regardless of how far the CPI fell.

How is the TIPS break-even rate useful for investors? The break-even rate is the implied inflation expectation embedded in market prices. An investor comparing a nominal Treasury to a TIPS of the same maturity can use the break-even to determine which is more attractive: if their personal inflation forecast exceeds the break-even, TIPS offer a better real return; if inflation is expected to come in below the break-even, nominal Treasuries win.

Why did long-dated TIPS lose money in 2022 despite high inflation? TIPS protect against inflation but still carry real interest-rate risk. In 2022, real yields rose sharply as the Fed tightened monetary policy and real rates normalized from historically negative levels. Rising real yields caused TIPS prices to fall significantly, overwhelming the inflation adjustment benefit, particularly for long-duration TIPS with high real-rate sensitivity.

Are I Bonds the same as TIPS? No. I Bonds are non-marketable savings bonds sold directly by the Treasury, with a fixed real rate plus a semi-annual inflation adjustment. They cannot be traded in the secondary market, have annual purchase limits per person, and have their own early-redemption penalties. TIPS are marketable, trade on exchanges and OTC, and have no annual purchase limit for auction participants.

How does the two-month CPI lag in TIPS affect performance comparisons? The reference CPI used in daily TIPS pricing is lagged by approximately two months. In a sudden inflation spike, TIPS buyers today will see their principal adjust for the CPI level from two months ago, not today. For very short holding periods, this lag creates a difference between actual CPI and the inflation immediately credited, which matters most in volatile inflation environments.

Sources

1. TreasuryDirect. "Treasury Inflation-Protected Securities (TIPS)." https://treasurydirect.gov/marketable-securities/tips/
2. TreasuryDirect. "Summary of Marketable Treasury Inflation-Protected Securities." https://www.treasurydirect.gov/laws-and-regulations/auction-regulations-uoc/inflation-protected-securities/
3. TreasuryDirect. "TIPS/CPI Data." https://treasurydirect.gov/auctions/announcements-data-results/tips-cpi-data/
4. PIMCO. "Understanding Treasury Inflation-Protected Securities." https://www.pimco.com/us/en/resources/education/understanding-treasury-inflation-protected-securities

Disclaimer

This article is educational content only and is not financial advice. Nothing here is a recommendation to buy, sell, or hold any security. Consult a licensed advisor before making investment decisions.