TIPS vs. I Bonds: What's the Difference?
Inflation quietly erodes the value of a fixed return, and the federal government offers two different instruments designed specifically to work around that problem. TIPS and I bonds share the same underlying goal, but they’re built so differently in terms of access, taxation, and liquidity that picking between them has less to do with which one is objectively better and more to do with what a saver actually needs the money to do.
The short answer
TIPS (Treasury Inflation-Protected Securities) and I bonds (Series I savings bonds) both adjust for inflation, but through different mechanics. TIPS trade on the open market, pay a fixed rate on a principal balance that itself rises and falls with inflation, and generate taxable income each year even though no cash arrives until maturity or sale. I bonds are non-marketable, blend a fixed rate with a semiannual inflation rate into one combined yield, and let interest accumulate untaxed until the bond is cashed. Which one fits better depends on how much a saver values liquidity, purchase size, and control over when taxes are due.
How each one adjusts for inflation
TIPS work by adjusting the underlying principal of the bond up or down with a widely tracked measure of consumer prices, then paying a fixed coupon rate on that adjusted principal twice a year. When inflation runs high, the interest payment grows because it’s a percentage of a larger principal; when prices fall, the principal — and payment — can shrink, though the bond won’t return less than its original face value at maturity. I bonds take a different route: the government sets a fixed rate that stays constant for the life of a given bond, then adds a separate inflation rate that resets twice a year based on recent price changes, and the two combine into a single composite rate applied to the bond’s value.
Purchase limits and where they’re held
This is where the two diverge sharply. TIPS can be bought through a brokerage account or directly from the government in large denominations, with no meaningful annual cap on how much an investor can hold. I bonds, by contrast, are subject to an annual purchase limit per person, set by the government and changing over time, which makes them a supplement to a portfolio rather than a primary building block for anyone trying to invest substantial sums. That limit is one of the clearest structural differences between the two.
Liquidity and how each one trades
TIPS are marketable securities, meaning they can be bought and sold on the secondary market before maturity, with a price that moves based on interest rate expectations as well as inflation expectations, similar to other treasury notes and bonds. That flexibility comes with the possibility of selling at a loss if rates have risen since purchase. I bonds can’t be sold to another party at all — they can only be redeemed back to the government, and redeeming one in the first several years after purchase carries an interest penalty, which makes them better suited to money that won’t be needed on short notice.
How the tax treatment differs
TIPS generate what’s sometimes called phantom income: the inflation adjustment to principal is taxable in the year it occurs even though the investor doesn’t receive that money until the bond matures or is sold, which can create a tax bill without matching cash in hand. I bonds avoid that problem because all of the interest, fixed and inflation-adjusted alike, is deferred until the bond is redeemed or reaches final maturity, giving the holder more control over which year the income shows up. As with any investment income, the tax rules involved depend on individual circumstances and can change over time.
The takeaway
Neither instrument is inherently the stronger choice — they solve overlapping but distinct problems. TIPS suit someone who wants inflation protection at scale with the option to trade in and out, while I bonds suit smaller, patient sums where deferred taxes and a government-backed floor matter more than liquidity. Understanding the structural trade-offs, rather than treating the two as interchangeable, is what makes it possible to see which one actually matches a given goal.