I Bonds vs Treasury Bills: Which Is Right for You?

When you have a chunk of cash sitting around and want it to work harder than your savings account, Treasury securities come up a lot. But there are different types, and I Bonds and Treasury bills (T-bills) are two of the most popular. They're both backed by the U.S. government, they're both safe, and they're both way better than letting money rot in a 0.01% savings account. But they work differently, and which one makes sense depends on your situation.

Let me walk you through how each one works, then help you figure out which is right for you.

How I Bonds Work

An I Bond (Series I Savings Bond) is a savings bond issued by the U.S. Treasury that protects you against inflation. Here's the magic: your interest rate has two components.

First, there's a fixed rate. Right now, that's 1.30% and it stays the same for the entire 30-year life of the bond. This floor is important — even if inflation disappears, you'll always earn at least 1.30%. Then there's an inflation rate that changes every six months (in May and November). It's based on the Consumer Price Index, and it's added on top of your fixed rate.

So if inflation is 3.50% right now, your combined rate would be around 4.80% (1.30% fixed + 3.50% inflation). But here's the key: if inflation drops to 1.5%, your rate drops to 2.80% (1.30% fixed + 1.50% inflation). You'll never earn less than the fixed rate, but you also won't lock in a super high rate if inflation cools down.

The math is simple: your actual interest = fixed rate + inflation rate, recalculated every six months. This is what makes I Bonds special — they're inflation-adjusted, so you're not getting hammered by rising prices eroding your returns.

I Bonds come with restrictions that matter for planning. You have to hold them for at least one year before you can cash them out. If you cash them out within five years, you lose three months of interest as a penalty. After five years, you can cash them anytime penalty-free. This five-year barrier is important because it discourages treating I Bonds like a savings account. They're meant for longer-term parking of money.

You buy I Bonds directly from TreasuryDirect.gov for as little as $25. You can buy up to $10,000 per calendar year online, plus an additional $5,000 if you buy with your tax refund. Paper bonds are no longer sold, but the online-only route is actually pretty convenient once you set up an account.

The earnings mechanism is straightforward: interest accrues daily and is compounded semiannually. That means every six months, your new interest calculation includes the interest you've already earned, compounding your growth. Over 30 years, this compounds into meaningful wealth.

How Treasury Bills Work

A Treasury bill (T-bill) is a short-term debt security issued by the U.S. Treasury. The shortest maturity is four weeks, and the longest is 52 weeks. You buy them at a discount to face value and get paid the full amount at maturity.

For example, you might buy a $10,000 T-bill for $9,950 and get $10,000 back in six months. That $50 difference is your interest. It sounds weird, but it's straightforward once you get used to it. The discount is the interest.

T-bills are purchased through TreasuryDirect or through a broker, and they're incredibly liquid. Your money is only locked up for a few weeks to a year depending on which maturity you choose. The current yields on T-bills are in the 4-5% range depending on maturity, which is pretty competitive when you consider the zero credit risk.

When you buy a T-bill, you're entering a straightforward transaction: lend money to the government, get it back with interest in a few weeks or months. No complexity. No inflation adjustment. Just guaranteed returns on a fixed timeline.

The interest is calculated based on the discount. A four-week bill might be sold at a 4.2% annual rate, meaning you'd buy it at about 99.96% of face value and get full value back in 28 days. A 52-week bill at 4.8% means you buy at about 95.2% of face value and get full value back in a year.

The Tax Implications (Why It Matters)

Both I Bond and T-bill interest is subject to federal income tax but not state income tax, which is an advantage compared to regular savings accounts where all interest is taxed at both levels. But there are differences in how they're treated and when you pay.

T-bill interest is fully taxable in the year you receive it. You get the T-bill back, you report the discount (interest) as income on your tax return. Simple, clear, and paid in the year received.

I Bond interest works differently. You can choose to report interest every year as it accrues, or you can defer federal tax until you redeem the bond or it matures (30 years). This is a huge tax-planning advantage. Many people buy I Bonds in lower-income years and redeem them in different years when they might be in a lower tax bracket. Or they defer for decades and handle the tax bill when they're ready. You might also be able to avoid tax entirely if you use I Bond proceeds for qualified education expenses — something called the education exclusion.

This tax deferral feature makes I Bonds particularly attractive for long-term wealth building because you're not paying taxes on compound growth until the very end.

The Head-to-Head Comparison

Liquidity matters. If you think you might need your money in the next year or two, T-bills are better. You can buy a 4-week or 13-week bill and be done with it. Your cash is tied up for weeks to months at most. I Bonds lock you in for at least a year, and you lose three months of interest if you pull out before five years. That's a real cost if plans change.

Predictability. T-bills give you an exact return upfront. You know exactly what you'll earn. There's no guessing, no adjustment at a future date. I Bonds are less predictable because the inflation component changes every six months. That's great if inflation stays high, but it's a headwind if we slip into deflation or low inflation. You're getting real inflation protection, but you're giving up certainty.

Rate environment matters for comparison. Right now, T-bill rates are around 4.5% for a one-year bill. I Bond rates are around 5.27% (as of early 2026), but remember that includes the current inflation adjustment. If inflation drops significantly, your I Bond rate will drop with it. A T-bill locks in your rate regardless of what happens to inflation. If you expect inflation to cool, T-bills might look better retrospectively. If you expect inflation to stay elevated, I Bonds look better.

Tax treatment. Both are federal-taxed but state-tax-free, which is a nice perk relative to regular savings accounts. I Bonds let you defer federal tax until redemption, which is a significant advantage for tax planning and wealth building. T-bills require reporting interest annually. Over a 30-year I Bond holding period, that deferral compounds meaningfully.

Minimum investment. I Bonds: $25. T-bills: $100 through TreasuryDirect. Both are incredibly accessible.

Versatility. T-bills are pure short-term vehicles. They're meant to roll over or ladder or hold briefly. I Bonds are meant for the long game. They're best for people who won't need the money and want inflation protection. They're not meant for frequent trading or short-term goals.

Which One Should You Choose?

Here's my honest take: Use I Bonds if you're saving for something 5+ years away and want inflation protection. They're perfect for a "set it and forget it" approach to medium-term to long-term savings. You're not worried about needing the money soon, and you want your purchasing power protected as inflation fluctuates. They're also great for kids' college funds or other long-horizon goals. You get tax deferral, guaranteed minimum return, and inflation protection all in one place.

Use T-bills if you want your money sooner or want certainty. You've got a big expense coming in a year. You're nervous about the economy and want a guaranteed rate that won't change. You like knowing exactly what you'll earn. Or you're building a "ladder" of T-bills that mature at different times so you have consistent access to cash without trying to time the market or figure out rolling purchases.

Stack both if you're being strategic. Many people use T-bills for their emergency fund buffer (beyond their liquid emergency fund) and I Bonds for longer-term savings. It diversifies your returns and your maturities. T-bills give you regular access to cash; I Bonds give you inflation protection and tax-deferred growth.

How to Actually Buy Them

For I Bonds: Go to TreasuryDirect.gov and create an account. It takes 10 minutes. You'll need your email, Social Security number, and bank account information for transfers. Once set up, you can buy I Bonds in any amount from $25 to $10,000 per calendar year (plus $5,000 if using tax refund). The purchase is immediate, and you get an electronic bond certificate. You can track your holdings and redeem anytime after one year through the same interface.

For T-bills: Also TreasuryDirect.gov. Same login. You specify the maturity (4-week, 13-week, 26-week, or 52-week), the amount (minimum $100), and submit a bid. The auction happens, you win at the discount price, and your cash is debited. When it matures, you get full value back plus the discount as interest. You can also buy T-bills through most brokers (Vanguard, Fidelity, Schwab, etc.) if you prefer a brokerage interface.

One pro tip: if you're trying to decide between a 13-week and 26-week T-bill, look at the rate difference. Sometimes a 26-week bill yields much more for only doubling your lockup period. The math might favor the longer maturity.

The Practical Strategy

If I had $20,000 to invest today, here's what I'd do: I'd put $10,000 into I Bonds because that's my annual limit and I'm not touching it for five years. The inflation protection and tax deferral are worth it. Then I'd split the other $10,000 into a ladder of T-bills—maybe $3,000 in a 13-week bill, $3,000 in a 26-week bill, and $4,000 in a 52-week bill. That way I get some inflation protection, some certainty, and access to cash at different points without having to sit around trying to time anything.

This ladder approach means every few months, a T-bill matures and I get cash back. I can then decide whether to reinvest in new T-bills, use the cash, or redirect it elsewhere. It's flexible without being chaotic.

The Bottom Line

Both are safer than the stock market and way better than letting cash languish in a checking account. Start at TreasuryDirect.gov and set up an account. It takes 10 minutes, and you'll be on your way to making your money work smarter.

The best investment is always the one that matches your timeline and risk tolerance. For most people saving for medium-term goals without high risk tolerance, I Bonds and T-bills are the unsung heroes of personal finance. They're boring, safe, government-backed, and way more effective than most people realize.