What is a Series I Bond
A Series I Bond is a U.S. government savings bond that earns interest tied to inflation, making it a safe, low-risk investment that protects purchasing power when inflation is high.
A Series I Bond (commonly called an "I Bond") is a savings bond issued by the U.S. Treasury that earns interest based on a combination of a fixed rate and an inflation-adjusted rate. Because part of the return is pegged to the Consumer Price Index (CPI), I Bonds protect purchasing power during inflationary periods — when inflation is high, the interest rate rises; when inflation falls, so does the rate.
I Bonds became a household topic in 2022 when their composite interest rate hit 9.62% — the highest in their history — during the sharp inflation surge of that period. Millions of Americans who had never heard of them rushed to buy the annual maximum at TreasuryDirect.gov.
How I Bond Interest Rates Work
The composite I Bond rate has two components:
| Component | Description |
|---|---|
| Fixed rate | Set at purchase; stays the same for the life of the bond |
| Inflation rate | Adjusted every May and November based on the CPI-U |
| Composite rate | Fixed rate + (2 × inflation rate) + (fixed rate × inflation rate) |
The Treasury announces new rates each May and November. The composite rate you receive adjusts every 6 months from your purchase date — not on a fixed calendar schedule.
I Bond Purchase Rules (2025)
| Rule | Detail |
|---|---|
| Annual purchase limit | $10,000 per Social Security number (electronic) |
| Paper bond option | Up to $5,000 additional via tax refund |
| Minimum purchase | $25 (electronic), $50 (paper) |
| Where to buy | TreasuryDirect.gov |
| Minimum hold period | 12 months |
| Early redemption penalty | Forfeit last 3 months of interest if redeemed before 5 years |
| No penalty redemption | After 5 years |
When I Bonds Make Sense
I Bonds are best used as:
- Emergency fund supplement — After the 12-month lockup, they can serve as a high-yield cash equivalent
- Short-to-medium term savings — For money you don't need for 1–5 years
- Inflation hedge — To preserve purchasing power in savings you'd otherwise keep in a savings account
- Low-risk diversification — Backed by the full faith and credit of the U.S. government; essentially zero default risk
I Bonds are not ideal for:
- Money you might need within 12 months (you can't redeem them at all during that period)
- Long-term growth (inflation-pegged returns trail stocks over long time horizons)
- Accounts above the $10,000 annual limit (other instruments like Treasury Inflation-Protected Securities (TIPS) are available through brokerages for larger amounts)
I Bond Tax Treatment
- Interest is exempt from state and local taxes
- Federal income tax is deferred until you redeem the bond or it matures (30 years)
- If used for qualified education expenses, interest may be federal tax-exempt (income limits apply)
The tax deferral is a meaningful benefit — rather than paying taxes on interest each year (as you would with a high-yield savings account), you pay all at once when you redeem. This is particularly valuable in high-income years if you plan to redeem during a lower-income year (like retirement).
I Bonds vs. High-Yield Savings Accounts
When I Bond rates are above current high-yield savings account rates, they're more attractive. When rates fall (as they did in late 2023 and 2024), high-yield savings accounts may pay comparable or more. Always compare the current I Bond composite rate at TreasuryDirect.gov to rates available on platforms like Marcus, Ally Bank, or Discover.