Series I Bond Tax Treatment

Interest earned on Series I savings bonds is subject to federal income tax, but the timing and ultimate tax burden depend on how you elect to report the interest and whether you meet the education exclusion criteria. Most investors defer reporting until redemption or maturity, but the IRS offers a tax-free pathway if bond proceeds fund qualified education expenses.

The basic tax rule: federal, not state

Interest accrued on Series I bonds is subject to federal income tax. When you buy an I bond for $50, it gradually grows in value through accrual of inflation-indexed interest. That accrual is taxable income, even though you have not yet received a check.

State and local income taxes do not apply to I bond interest. This is an advantage over corporate bonds and many municipal bonds, which are taxable at the state level.

The question is when you report the interest. The IRS offers two elections.

Election 1: Defer reporting until redemption

By default, you can report I bond interest when you redeem the bond or when it matures (after 30 years). This is called the accrual method or deferred reporting.

Example: You buy a $10,000 I bond in January 2026. By January 2031 (five years), the bond is worth $11,200 (due to inflation adjustment and composite interest rate). If you redeem it then, you report $1,200 of interest income on your 2031 tax return, at your marginal tax rate for that year.

This deferral is powerful: it allows decades of tax-free compounding. An investor can buy I bonds in their working years, redeem them in retirement (when income is lower and the tax bracket is lower), and pay less total tax.

The IRS does not require you to report interest in any year until you actually cash the bond. The interest is still accruing and compounding; it just stays off your tax return.

Election 2: Elect annual accrual reporting

Alternatively, you can elect to report I bond interest each tax year, even though you have not redeemed the bond. This is done via Form 3115 (Application for Change in Accounting Method), filed with your first tax return including I bond interest.

Once you elect annual reporting, you must continue reporting interest annually until the bond matures or you redeem it. You cannot switch back to deferral.

Why would you choose annual reporting? Rarely, and usually for estate planning. If you own a large quantity of I bonds and expect to pass them to heirs, annual reporting locks in a known tax basis. When you die, your heirs step up to a new cost basis (the bond’s fair value on your death date). Without annual reporting, your heirs would owe tax on decades of accumulated interest when they redeem; with annual reporting, the stepped-up basis applies, and they pay little or no tax on interest accrued after your death.

For most retail investors, annual reporting is unnecessary complexity.

The education exclusion: pathway to tax-free interest

The IRS allows a 100% exclusion of I bond interest if all of the following conditions are met:

1. Bondholder age. The person in whose name the bond is registered must be at least 24 years old at the time of purchase.
2. Bond owner pays education expenses. The bond owner (not a parent funding a child’s college) must use the bond proceeds to pay qualified education expenses in the same tax year the bond is redeemed.
3. Qualified expenses. The expenses must be tuition, fees, and room & board at an accredited post-secondary school, or contributions to a Coverdell ESA or 529 plan.
4. Income cap. The exclusion phases out if your modified adjusted gross income (MAGI) exceeds $92,550 (2026, single) or $146,550 (married filing jointly). Above those limits, the exclusion is zero.

If you meet these criteria, you can redeem an I bond, pay for tuition, and report zero interest income. The entire gain is tax-free.

Example: Jennifer, age 28, buys $50,000 of I bonds in 2026. She pays $50,000 cash upfront. By 2030, the bonds are worth $55,000 (interest = $5,000). She redeems the bonds, pays $55,000 in tuition for her master’s degree, and reports zero interest income on her 2030 tax return. The $5,000 gain is completely excluded.

The catch: you must redeem and use the proceeds in the same tax year. If Jennifer redeems in 2030 but pays tuition in 2031, the exclusion does not apply.

Reporting on your tax return

If you report deferred interest (the common case), the interest is included in your income on your Form 1040 in the year you redeem the bond. The issuer (the U.S. Department of the Treasury) reports the interest on Form 1099-INT sent to you around January 31 of the following year. You report it as ordinary income, not capital gain.

If you elect annual reporting, you report a portion of accrued interest each year, even though you have not received a redemption.

If you qualify for the education exclusion, you exclude the interest on your return; it is not reported as income.

Lost basis at death

I bonds have a significant tax-planning pitfall. If you die holding I bonds, your heirs inherit them with a stepped-up cost basis at fair value as of your death date. But if you had been deferring interest reporting, your executor must report all of the accumulated (unaccrued) interest on your final tax return—a potentially large surprise tax bill due to the estate.

If you had instead elected annual reporting, the interest would have been spread over decades, and your heirs would step up with a known basis, avoiding the lump-sum tax hit.

This is why some estate planners recommend annual reporting for large bond holdings, even though it is administratively annoying.

Redemption penalties and timing

Series I bonds cannot be redeemed in the first 12 months after purchase. If redeemed before 5 years, you forfeit the last 3 months of interest. This is not a tax issue but a yield issue: it reduces the effective return if you have a short time horizon.

Tax brackets and strategic timing

Since I bond interest is ordinary income, it is taxed at your marginal rate. A retiree in the 12% bracket will owe 12% tax on interest; a high earner in the 37% bracket will owe 37%.

Because interest can be deferred until redemption, a savvy investor can time the redemption in a low-income year (e.g., a year with little business income, or the year after retirement) to minimise the tax rate.

Example: A self-employed accountant earns $200,000 in 2025 and is in the 24% tax bracket. She bought I bonds years ago and has $100,000 of accrued interest. If she redeems in 2025, she pays 24% tax = $24,000. But in 2026, she takes a sabbatical and has minimal income. If she redeems in 2026, she may be in the 12% bracket, paying only $12,000 in tax. The deferral option allows her to control this outcome.

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