Wait until April 10 if you can — that’s when March CPI drops and you can calculate the new May rate before committing.

There are exactly three weeks where the I Bonds May 2026 rate decision matters. After April 30, it’s made for you.

TIPSWatch published its March 29 projection: the fixed rate component is expected to hold at 0.90% when Treasury resets I Bond rates on May 1. That’s the more predictable piece. The variable inflation component — the piece that actually drives most of your return — won’t be known until the Bureau of Labor Statistics releases March CPI-U data on April 10.

That creates a narrow window where you’re making a bet with incomplete information. Buy before April 30 and you lock in the current composite rate for your first six months. Wait until May 1 and you get the new rate from day one. Neither choice is obviously wrong.

I bought $5,000 in I Bonds back in January. Now I’m sitting on the remaining $5,000 of my annual limit, trying to figure out the same thing you are.

Here’s what the math says.

Quick Decision Table

Scenario	Buy Before April 30	Wait Until May 1
First 6 months rate	Current composite (known)	New composite (unknown until April 10)
Next 6 months rate	Automatically switches to May rate	May rate continues
Fixed rate	Current 0.90% locked for life of bond	Projected 0.90% (same, per TIPSWatch)
Variable component	Current semiannual inflation rate	New rate based on March CPI-U
Best if	You think inflation is cooling (new variable rate will be lower)	You think inflation is running hot (new variable rate will be higher)
Annual limit	$10,000 electronic + $5,000 paper (tax refund)	Same

The one-line version: If the fixed rate holds at 0.90% both ways — and TIPSWatch’s projection says it will — the entire decision hinges on whether you think the next six months of inflation will be higher or lower than the current six months. April 10 gives you the answer.

How I Bond Rates Work: The May 2026 Reset Explained

I Bonds have two pieces that combine into one composite rate. Most people mix these up.

Fixed rate: Set by Treasury twice a year (May 1 and November 1). Once you buy, your fixed rate stays locked for the life of the bond — up to 30 years. The current fixed rate is 0.90%. TIPSWatch projects the May reset will keep it at 0.90%, based on the spread between TIPS real yields and Treasury nominal yields.

Variable rate (inflation component): Also resets twice a year, based on changes in the CPI-U (Consumer Price Index for All Urban Consumers). This part adjusts to actual inflation. If inflation runs at 3% annualized, the variable component is roughly 3%. If inflation drops to 1.5%, so does this piece.

Composite rate formula:

Composite = Fixed rate + (2 x semiannual inflation rate) + (fixed rate x semiannual inflation rate)

In practice, you can approximate it as: fixed rate + annualized inflation rate. The cross-product term is small.

The key mechanic most people miss: When you buy, you get the current composite rate for your first six months regardless of when the next reset happens. Then you automatically switch to whatever the new rate is. So a purchase on April 29 locks in the current rate until late October, then shifts to the May rate. A purchase on May 1 gets the May rate from the start.

You’re not choosing between two rates forever. You’re choosing which rate applies to your first six months.

The April 10 CPI Release Is the Real Deadline

Here’s why I’m not buying yet.

The March CPI-U data drops on April 10. That release determines the semiannual inflation component for the May 2026 through October 2026 I Bond rate. Once it’s published, you can calculate the new composite rate yourself — Treasury won’t officially announce until May 1, but TIPSWatch and other trackers will post the projected number within hours of the CPI release.

That gives you a 20-day window (April 10 to April 30) where you know both rates and can make an informed decision. Right now, you’re guessing.

What the CPI Could Show

If March CPI comes in hot (above 0.3% month-over-month): The new variable rate will likely be higher than the current one. Waiting until May 1 means getting that higher rate from day one for six months instead of only getting it after your first six months expire. In that case, waiting wins — but only by a small margin, since you’d switch to the higher rate in October anyway.

If March CPI comes in cool (below 0.2% month-over-month): The new variable rate drops. Buying before April 30 locks in the current (higher) rate for your first six months before you’re forced to switch to the lower May rate. Buying early wins.

If it’s a wash (0.2-0.3%): Doesn’t matter much either way. The difference over six months on $10,000 is probably $15-30. Not worth losing sleep over.

My plan: wait for April 10, calculate the projected May composite rate, and decide with actual data instead of CPI guesses. If you want to do the same, bookmark TIPSWatch and check it the evening of April 10.

The Crossover Math: I Bonds vs CDs

This is the comparison that almost never shows up in I Bond articles, and it’s the one that actually matters for most people reading this.

I wrote about T-bills vs CDs after taxes last week. I Bonds add another layer of complexity because their return depends on future inflation — which nobody knows.

But we can calculate the breakeven.

Current best 12-month CD rate: ~4.20% (see our CD roundup)

I Bond fixed rate: 0.90%

Question: What annualized inflation rate makes the I Bond composite rate match a 4.20% CD?

4.20% = 0.90% + inflation rate (approximately)

Inflation rate needed: ~3.30%

If annualized CPI inflation runs above 3.3% over your I Bond holding period, the I Bond beats the CD. If inflation runs below 3.3%, the CD wins on total yield.

Where Is Inflation Right Now?

The February 2026 CPI-U showed year-over-year inflation at roughly 2.8%. That’s below the 3.3% crossover point. At current inflation, a 4.20% CD is paying more than an I Bond.

But the CD rate is locked. If the Fed cuts in December and CD rates drop to 3.5% next year while inflation ticks back up to 3.5%, the I Bond adjusts upward and the CD doesn’t. You’re comparing a fixed return against an inflation-indexed one. They’re different bets.

Inflation Scenario	I Bond Composite (approx.)	4.20% CD	Winner
2.0% inflation	~2.90%	4.20%	CD by 1.30%
2.8% inflation	~3.70%	4.20%	CD by 0.50%
3.3% inflation	~4.20%	4.20%	Tie
4.0% inflation	~4.90%	4.20%	I Bond by 0.70%
5.0% inflation	~5.90%	4.20%	I Bond by 1.70%

The honest read: At current inflation levels, CDs win on raw yield. I Bonds are the better bet only if you think inflation is heading higher — and right now, the market consensus is that it’s heading sideways or slightly lower through 2026.

Who Should Buy I Bonds Anyway

Even when CDs win on headline yield, I Bonds have structural advantages that make them the right call for specific situations.

Tax deferral. I Bond interest isn’t taxed until you cash out (or the bond matures in 30 years). That’s federal tax deferral you don’t get with CDs or T-bills. If you’re in a high bracket now and expect to be in a lower bracket later (retirement, career break, gap year), that deferral is real money.

State tax exemption. Like T-bills, I Bond interest is exempt from state and local income taxes. If you live in California or New York, the effective after-tax advantage is meaningful — the same math I walked through in the T-bills vs CDs comparison applies here too.

Inflation hedge for emergency reserves. I keep a portion of my emergency fund in I Bonds specifically because they can’t lose to inflation over the long term (assuming you hold past the 1-year minimum and 5-year early withdrawal penalty window). A high-yield savings account pays 4.20% today but could pay 2.5% next year if the Fed cuts aggressively. I Bonds adjust.

Education expense planning. If you meet the income limits, I Bond interest used for qualified education expenses can be completely tax-free at the federal level. That’s a perk that CDs, T-bills, and savings accounts can’t match.

The Purchase Limits (And the Paper Bond Trick)

The cap trips people up every year.

• $10,000 per person per calendar year — electronic purchases through TreasuryDirect.gov
• $5,000 per person per calendar year — paper I Bonds purchased with your federal tax refund (IRS Form 8888)

That’s $15,000 total per person. For a married couple filing jointly, that’s $30,000 — $20,000 electronic and $10,000 paper via tax refunds.

You can also buy $10,000 per entity (trusts, LLCs, etc.), which is how some people push the limits higher. But for most people, $10,000-$15,000 per year is the practical cap.

One thing I didn’t realize until my second year buying I Bonds: the calendar year limit resets on January 1, not on the rate reset dates. If you haven’t bought any I Bonds in 2026 yet, you have the full $10,000 available right now. If you bought $5,000 in January (like I did), you have $5,000 remaining.

The Actual Buy-or-Wait Flowchart

Here’s how I’m thinking about it. Step by step.

1. Have you already used your $10,000 electronic limit for 2026? If yes, you’re done until next year. If you have tax refund dollars, consider the paper option.

2. Can you wait until April 10? If yes, wait. The CPI release gives you the data to calculate the May composite rate. No reason to guess when you can know.

3. After April 10, is the new composite rate higher than the current one? If yes, wait until May 1 to buy at the higher rate. If no, buy before April 30 to lock in the current higher rate for your first six months.

4. Is the I Bond composite rate (either current or projected May) higher than your best available CD rate minus your state tax rate? If yes, the I Bond wins after tax. If no, put the money in a CD or T-bill ladder instead.

5. Do you value the inflation hedge more than the guaranteed fixed return? This is the gut-check question. If you think inflation could surprise to the upside over the next 1-5 years — tariff impacts, supply chain disruptions, sticky services inflation — I Bonds provide a floor that CDs don’t. If you think inflation is tamed and rates are heading down, the 4.20% CD locks in a great return.

What I’m Doing

Waiting until April 10. That’s the whole plan.

I already have $5,000 in I Bonds from January at the current composite rate. For my remaining $5,000 of annual limit, I want to see the March CPI number before deciding. If the new rate looks lower than the current one, I’ll buy on April 11. If it looks higher, I’ll wait until May 1 or 2.

The fixed rate holding at 0.90% both directions makes this a pure inflation call. And I’d rather make that call with data than with a forecast.

I also have $15,000 in a T-bill ladder that I’m keeping separate. I Bonds and T-bills serve different purposes in my portfolio — the T-bills are for money I might need in 4-13 weeks, the I Bonds are for long-term savings I won’t touch for at least five years.

The Bottom Line

The May 2026 I Bond rate reset is a non-event if the fixed rate holds at 0.90% as projected. The real variable is inflation, and you’ll know that variable on April 10.

Don’t buy before April 10 unless you’re worried about forgetting. Do buy before April 30 if the new rate looks lower and you want six months at the current rate. Wait until May 1 if the new rate looks higher.

And be honest about the CD comparison. At current inflation (~2.8%), a 4.20% CD is beating I Bonds on raw yield. I Bonds only pull ahead if inflation rises above 3.3% — and right now, that’s not the consensus. The case for I Bonds isn’t yield. It’s the tax deferral, the state tax exemption, and the insurance policy against inflation you’re not expecting.

For $10,000 or less per year, that insurance policy is worth having. But it’s insurance, not an investment strategy.

TreasuryDirect.gov. April 10 CPI release. Then decide.

---

I Bond rates and projections based on TIPSWatch analysis published March 29, 2026 and current Treasury data. CPI release date per BLS schedule. This is not financial or tax advice — consult a qualified professional for your specific situation. I hold I Bonds purchased in January 2026.