Data downloads

The core series behind this site, as stable CSVs.

Stable URLs, plain CSV, rebuilt from the live Treasury APIs on the site's cadence (see About). Free to use and cite with a link to savingsbondcheck.com; the underlying data is US-government public domain.

i-bond-rate-history.csv

Every semiannual I bond rate period since September 1998: the fixed rate assigned to new issues, the semiannual inflation rate, and the composite rate for new issues. Source: Treasury Fiscal Data, I Bonds Interest Rates.

• period_start — first day the announced rates apply (YYYY-MM-DD)
• period_end — last day of the announcement period
• fixed_rate_new_issues_pct — lifetime fixed rate for bonds bought in this period (%)
• semiannual_inflation_rate_pct — semiannual inflation rate (%)
• composite_rate_new_issues_pct — annualized composite rate for new issues (%)

i-bond-rates-by-issue-month.csv

Every I bond issue month since September 1998 with its lifetime fixed rate and its combined rate under the May 2026 announcement (each bond adopts it at its own semiannual reset). Source: Treasury Fiscal Data, I Bonds Interest Rates.

• issue_year_month — issue cohort (YYYY-MM)
• fixed_rate_pct — lifetime fixed rate (%)
• combined_rate_2026_05_pct — combined rate under the May 2026 announcement (%)

ee-bond-final-maturity.csv

Series EE final-maturity schedule by issue year (30-year rule) with earning status as of the build date and the doubling-guarantee rule for the era. Source: TreasuryDirect EE bond pages.

• issue_year — calendar year of issue
• final_maturity_year — year the bond stops earning (issue month + 30 years)
• status — matured / maturing this year / earning, as of the build date
• guarantee_rule — original-maturity or doubling guarantee rule(s); pipe-separated when the year spans two eras

matured-unredeemed-savings-bonds.csv

Monthly total of matured, unredeemed US savings securities from the Monthly Statement of the Public Debt, Table III (2001–present).

• record_date — MSPD statement date (month end)
• matured_unredeemed_millions — matured unredeemed savings securities, $ millions