The Bond Fund That Inflation Walks Right Through
A normal bond pays you a fixed coupon. That number is locked the day you buy it and never moves again, no matter what happens to prices in the real world. If you bought a 10-year Treasury paying 3% and inflation then runs at 6% for a few years, you’re earning 3% nominal and losing roughly 3% a year in purchasing power. The bond did exactly what it promised. It just promised the wrong thing for the environment you ended up in.
That’s the specific hole I Bonds and TIPS are built to fill. Neither is a replacement for your total bond fund in general. Both exist for one job: making sure inflation doesn’t quietly eat the real value of money you were counting on to still buy the same amount of stuff later. If you already read the piece on when to add bonds to your portfolio at all, you know the case for holding bonds in the first place. This one is narrower: once you’ve decided you want inflation protection specifically, here’s how the two instruments that provide it actually work, and which fits which situation.
I Bonds: The Government Savings Bond With a Split Personality
An I Bond’s interest rate is really two rates stapled together, and understanding the split is the whole game.
The fixed rate is set the day you buy and stays with that bond for its entire 30-year life, even as new fixed rates get announced for future purchases. This is the part that differentiates one I Bond purchase from another. Buy in a month with a good fixed rate and you’ve locked in real purchasing-power growth above inflation for three decades. Buy in a month with a fixed rate of 0% and your bond just tracks inflation, forever.
The variable rate is based on CPI and resets every six months, in May and November. It’s identical for every I Bond in existence regardless of when you bought, so it doesn’t reward good timing the way the fixed rate does.
The two combine into a composite rate: fixed rate + (2 x semiannual inflation rate) + (fixed rate x semiannual inflation rate). Plug in a purely hypothetical fixed rate of 1.2% and a hypothetical semiannual inflation reading of 1.5%, and you get a composite rate of about 4.22% for that six-month period. Don’t treat either number as current: look up the actual published rates at TreasuryDirect.gov before you buy, since both halves reset on a schedule.
Because the variable half is the same for everyone, the fixed rate is what long-term holders should actually be watching. It’s the only lever that separates one purchase month from another.
The Mechanics You Need to Know Before You Buy
Purchase limits. The commonly cited limit is $10,000 per person per calendar year in electronic I Bonds through TreasuryDirect, with an additional $5,000 available in paper bonds if you direct part of a federal tax refund that way. Confirm the current figures before you buy: these are a policy choice, not a law of physics, and the government could change them.
TreasuryDirect.gov is the only place to buy them, and the interface has a well-earned reputation for feeling like it was built for a different decade. Budget some patience for account setup: not complicated, just ugly and unforgiving if you fumble a form.
The one-year lockup is absolute. You cannot redeem an I Bond for any reason during the first 12 months. Not an emergency, not a family situation, nothing. If there’s a real chance you’ll need this specific money inside a year, it doesn’t belong in an I Bond.
The three-month penalty runs from year one to year five. Redeem between month 12 and month 60 and you forfeit the last three months of interest. Redeem at or after five years and there’s no penalty at all. Concretely: if your bond is earning around $36 a month in interest at the point you cash out early, you’re giving up roughly $108 to do it, a fixed haircut you can estimate yourself from the balance and rate shown on your TreasuryDirect account page.
Tax Treatment Is Where I Bonds Get Interesting
Interest on I Bonds is exempt from state and local income tax everywhere, which matters more if you live somewhere with a real state tax bill.
Federal tax is where it gets useful. You have a choice: report interest annually as it accrues, or defer all of it until you actually redeem the bond or it matures. Almost everyone should defer. You’re not paying tax on money you haven’t received yet, and the deferral can span decades if you hold to the 30-year maturity.
There’s also an education exclusion: redeem I Bonds to pay qualified higher education expenses and the interest can come out federally tax-free, subject to income limits that phase the benefit out at higher earnings. Check the current thresholds against your own return before counting on it.
The deferral is where this gets interesting for a high earner. Say you’re stacking RSU vests and bonuses into a high marginal bracket right now. An I Bond lets you push the tax bill on years of accrued interest into whatever year you choose to redeem, ideally a year after you’ve cut back hours, taken a sabbatical, or retired, when your marginal rate is lower. You choose which year’s bracket the interest lands in, and for someone confident their income drops later, that’s a real, quantifiable advantage.
TIPS: The Same Idea, Traded Like a Bond
Treasury Inflation-Protected Securities solve the same core problem as I Bonds, inflation eating your real return, but with a completely different mechanism and a completely different risk profile.
With TIPS, the principal adjusts with CPI, not just the interest rate. As inflation rises, your principal balance grows; the fixed coupon rate then applies to that larger, adjusted principal, so your actual interest payment grows too. At maturity you get back the greater of the inflation-adjusted principal or your original principal, so there’s a floor against deflation on the principal itself.
You can buy TIPS directly at Treasury auction, on the secondary market through a brokerage, or through a fund (SCHP and VTIP are common low-cost choices), a meaningfully different access model than I Bonds, which only exist as an individual, non-tradeable purchase through TreasuryDirect.
The critical difference that trips people up: TIPS can lose value in the short term. Because they trade on the secondary market, their price responds to changes in real interest rates, the same way any bond’s price responds to rate changes. If real yields rise after you buy, the market price of your TIPS holding falls, even though the inflation-adjustment mechanism is working exactly as designed. I Bonds never do this: an I Bond’s redemption value never drops in nominal terms, period.
The Phantom Income Problem
This is the part that makes TIPS a bad fit for a regular brokerage account. The inflation adjustment to your principal is taxable as ordinary income in the year it accrues, federally, even though you don’t actually receive that money until the bond matures or you sell it.
Concretely: a $10,000 TIPS position that accrues a 3% inflation adjustment in a given year generates $300 of taxable phantom income that year. At a 32% marginal federal rate, that’s $96 of tax owed on money you never touched, a real check written against income you haven’t collected yet.
The fix is straightforward: hold TIPS in a tax-advantaged account, a traditional or Roth IRA, or a 401(k) that offers a TIPS fund option. Inside those accounts the phantom income problem disappears because nothing is taxed until (or never, for Roth) withdrawal. TIPS held directly in a taxable brokerage account are one of the few places where the “just hold index funds and forget about it” default backfires on you.
Breakeven Inflation: How to Actually Decide
The way professionals size up whether TIPS or a plain nominal Treasury is the better bet is the breakeven inflation rate: the gap between a nominal Treasury’s yield and a TIPS of the same maturity’s real yield.
Hypothetically, if a 10-year nominal Treasury yields 4.5% and a 10-year TIPS yields 2.2% real, the breakeven is 2.3%. That number is the market’s implied forecast for average annual inflation over that decade. If you believe actual inflation will run above 2.3% over the period, TIPS wins, since you’d be capturing more than the market is pricing in. If you believe inflation will run below 2.3%, the plain nominal Treasury wins, since you locked a higher fixed rate than inflation ends up justifying.
The breakeven rate is published and updated constantly (it’s the same math the Fed and every bond desk watches), so you’re never guessing blind. You’re deciding whether you think inflation runs hotter or cooler than the market currently expects, using a real number as your baseline.
When Each One Actually Wins
I Bonds win when: you want a hard floor against ever seeing a nominal loss, you’re comfortable with the purchase limit and the illiquidity, and you’re either using tax-advantaged deferral strategically or you’d rather skip brokerage tax reporting on phantom income entirely. You buy a fixed dollar amount, lock it away, and it grows.
TIPS win when: you need more than $10,000 a year of inflation-protected exposure (a real constraint for anyone building a meaningful allocation), you want the money in a retirement account where phantom income is a non-issue, or you want the flexibility to sell before a fixed lockup period. TIPS funds also diversify across maturities automatically, which individually held I Bonds cannot do.
Who Should Skip Both
If you’re more than a decade from needing this money and still in heavy accumulation mode, you probably don’t need inflation protection yet. Equities have historically outrun inflation by a wide enough margin over long horizons that holding TIPS or I Bonds early just costs you expected growth, for a risk that matters more closer to when you’ll actually spend the money. Inflation protection is a tool for a specific, bounded window, not a permanent core holding for a 30-year-old with two decades of runway.
If your emergency fund is already sitting in a high-yield savings account earning a competitive rate, adding I Bonds on top for the same purpose is often just complexity without a real return improvement, especially once you account for the one-year lockup taking that money off the table for actual emergencies.
Practical Recommendation by Use Case
Emergency fund overflow (the slice beyond what you’d need in the next year): I Bonds are a reasonable secondary layer, never the primary layer. Keep your true emergency reserve in a high-yield savings account where it’s available same-day. Money you’re fairly confident you won’t touch for at least a year can go into I Bonds up to the annual limit as a higher-yielding, inflation-linked parking spot. Never put your entire emergency fund into I Bonds given the one-year lockup.
A known expense several years out (a home down payment, a kid’s tuition, a planned sabbatical): TIPS held in a fund or a bond ladder timed to the expense date make sense, especially inside a tax-advantaged account if you have room. You get inflation protection matched to a real deadline without the annual purchase cap getting in your way, since a goal like a down payment usually needs more than $10,000 a year of coverage.
A retirement bond allocation: a TIPS allocation (or a fund like SCHP or VTIP) inside your 401(k) or IRA is the natural long-term home. This is exactly the scenario the breakeven inflation rate is built for: deciding, as part of a broader glide path, how much of your fixed-income sleeve should be inflation-linked versus nominal. I Bonds can supplement this at the margins, particularly for a high earner planning to redeem in a lower-bracket retirement year, but the $10,000 annual cap means they’ll never carry the load alone.
The Bottom Line
A plain bond fund protects you from recessions and market crashes. It does nothing if inflation runs hot, because the coupon is fixed while the value of that number quietly shrinks. I Bonds and TIPS are the two tools the Treasury built for that specific risk, and they’re not interchangeable. I Bonds are simple, capped, illiquid for a year, and get more useful the more control you want over which tax year the interest lands in. TIPS scale higher, trade daily, can dip in price before maturity, and demand a tax-advantaged account to avoid paying tax on income you haven’t received yet.
Neither belongs in your portfolio at 28 with two decades of runway ahead of you. Both belong once you’ve got a real dollar amount and a real date you’re protecting: an emergency fund overflow, a tuition bill five years out, a retirement bond sleeve you’re finally old enough to care about. Match the tool to the deadline, check the actual current rates before you buy either one, and stop treating “bonds” as a single undifferentiated blob that all does the same job.
