I Bonds: Composite Rate Formula, Limits, and Tax Rules

9.62% — The Rate That Sent Millions to TreasuryDirect

When the U.S. Treasury announced a 9.62% annualized composite rate for Series I savings bonds in May 2022, demand overwhelmed the TreasuryDirect website, causing extended outages as investors rushed to purchase the inflation-linked instruments. It was the highest I bond rate since the series launched in 1998. For a brief period, I bonds outperformed virtually every investment vehicle in the United States on a risk-adjusted basis — backed by the full faith and credit of the federal government, exempt from state and local income tax, and guaranteed never to lose nominal value. Understanding the rate formula and the rules that govern I bonds separates informed buyers from those who simply chased the 2022 headline.

Series I savings bonds are non-marketable government securities sold directly by the U.S. Treasury through TreasuryDirect.gov. They cannot be bought or sold on a secondary market. They cannot be used as loan collateral. They accrue interest monthly and compound semiannually. The minimum purchase is $25 (electronic) and the maximum per Social Security number per calendar year is $10,000 in electronic form, plus an additional $5,000 in paper I bonds purchased using a federal income tax refund — for a total maximum of $15,000 per individual annually.

The Composite Rate Formula

The composite rate has two components that are announced by the Treasury each May and November. The fixed rate is set at issuance and remains constant for the life of the bond — it has ranged from 0% to 3.60% historically and reflects the real yield the Treasury is willing to offer above inflation. The inflation rate component is calculated from the non-seasonally adjusted CPI-U (Consumer Price Index for All Urban Consumers) and changes every six months from the bond's issue date.

The exact formula published by Treasury is: Composite rate = [Fixed rate + (2 × Semiannual inflation rate) + (Fixed rate × Semiannual inflation rate)]. The cross-product term is small but not zero. When the semiannual CPI-U measurement is negative (deflation), the inflation component becomes negative and can reduce the composite rate below the fixed rate — but the composite rate can never fall below 0%. The bond will never lose nominal value. This floor guarantee is one of I bonds' defining features.

Lockup and Penalty Structure

I bonds cannot be redeemed for the first 12 months under any circumstances. No exceptions. After 12 months and before 5 years of holding, a redemption penalty equal to the most recent 3 months of interest applies. After 5 years, I bonds can be redeemed at full accrued value with no penalty. Bonds that are not redeemed stop earning interest after 30 years.

• 0–12 months: Cannot redeem under any circumstances
• 12–60 months (1–5 years): Redeemable with 3-month interest penalty
• 60+ months (5+ years): Redeemable at full value, no penalty
• 30 years: Bond matures and stops accruing interest

Strategically, the 3-month penalty is modest. An investor who purchased at 9.62% and holds for 13 months before redeeming sacrifices 3 months of the lower subsequent rate — likely still achieving a net yield of 6%–7%+ annualized, depending on when rates reset. Timing redemptions to avoid losing months of high-rate accrual is a common optimization among sophisticated I bond holders.

Tax Treatment and the Education Exclusion

I bond interest is subject to federal income tax but exempt from all state and local income taxes. Investors choose between two reporting methods:

• Cash method (default): Interest is taxable in the year of redemption — allowing years of tax-deferred compounding before the liability comes due
• Accrual method: Interest is reported annually as it accrues — rarely chosen since it accelerates taxation without benefit

An underutilized provision allows I bond proceeds used to pay qualified higher education expenses to be partially or fully excluded from federal income tax under Section 135. The exclusion phases out at modified adjusted gross income between $96,800 and $111,800 (single) and $145,200 and $175,200 (married filing jointly) in 2024. Bonds must be in the taxpayer's name (not the student's) and purchased in a year the taxpayer was at least 24 years old. Qualifying education expenses include tuition and fees at eligible institutions.

I Bond Purchases via Tax Refunds and Trusts

A married couple can therefore purchase up to $35,000 per year: $10,000 each electronically ($20,000), $5,000 via tax refund, plus an additional $10,000 through a revocable living trust with its own EIN. Some attorneys establish separate living trusts for each spouse specifically to maximize I bond purchasing capacity — a planning technique most relevant during high-rate environments.

This article is for informational purposes only and does not constitute financial advice.