I-Bond Rates API Reference

Overview

I-Bond Rates pulls data from the US Treasury Fiscal Data API. The composite rate consists of a fixed rate (set at purchase, never changes) plus an inflation rate (adjusts every May and November based on CPI). Historical rate data is available back to 1998.

Endpoint

One host, one path per API. The block below shows this call in four languages; every one of them is the same HTTP request. Making requests covers the timeouts, retries and parameter rules that apply to all of them. The SDKs wrap the same call in a typed client.

GEThttps://api.apiverve.com/v1/savingsbonds

curl "https://api.apiverve.com/v1/savingsbonds?period=2024-11" \
  -H "x-api-key: your_api_key_here"

const res = await fetch('https://api.apiverve.com/v1/savingsbonds?period=2024-11', {
  headers: { 'x-api-key': 'your_api_key_here' },
});

if (!res.ok) throw new Error(`${res.status} ${await res.text()}`);

const { data } = await res.json();
console.log(data);

import requests

res = requests.get(
    "https://api.apiverve.com/v1/savingsbonds?period=2024-11",
    headers={"x-api-key": "your_api_key_here"},
    timeout=15,
)
res.raise_for_status()

print(res.json()["data"])

package main

import (
	"fmt"
	"io"
	"net/http"
)

func main() {
	req, _ := http.NewRequest("GET", "https://api.apiverve.com/v1/savingsbonds?period=2024-11", nil)
	req.Header.Set("x-api-key", "your_api_key_here")

	res, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()

	out, _ := io.ReadAll(res.Body)
	fmt.Println(string(out))
}

Replace your_api_key_here with the key from your dashboard. When the inputs arrive as a list rather than one at a time, batch requests run up to 200 of them through this same API in a single call.

Authentication

Send your key in the x-api-key header. That is the only auth step — there is no token exchange and no per-endpoint scope to configure. Authentication covers creating, rotating and revoking keys.

401 is the only auth verdict

A 401 means the key is missing, invalid or expired. A 403 means the key is valid but not permitted here — blocked by a key restriction or an IP allow-list. Running out of credits is a 429.

Parameters

Sent in the query string. Premium parameters are accepted on every plan but only take effect on plans that include them.

Parameter	Type	Description
`period`OptionalPremium	string	Specific issue period to lookup (YYYY-MM format, e.g., 2024-11). Omit for current rates.

Response

Every API returns the same three top-level keys, so one response handler covers your whole integration: status, error and data. Only data changes shape. Response format covers the envelope, the other output formats and how premium fields are withheld.

Sample response

{
  "status": "ok",
  "error": null,
  "data": {
    "iBonds": {
      "currentRate": 5.27,
      "fixedRate": 1.3,
      "inflationRate": 1.97,
      "purchaseLimit": 10000
    },
    "eeBonds": {
      "currentRate": 2.7,
      "guaranteedDoubling": "20 years (guaranteed to double in value)",
      "purchaseLimit": 10000
    },
    "recommendation": "I Bonds",
    "recommendationReason": "I Bonds currently offer 5.27% vs EE Bonds at 2.70%",
    "nextRateChange": "2024-05-01",
    "lastUpdated": "2024-02-01T00:00:00.000Z"
  }
}

Response fields

Paths are relative to data. Premium fields are absent rather than zeroed on plans that do not include them, so check for presence instead of comparing to 0.

Field	Type	Example	Description
`iBonds`	object	`{...}`
`currentRate`	number	`5.27`
`fixedRate`	number	`1.3`	Fixed rate component (set at purchase, never changes)
`inflationRate`	number	`1.97`	Inflation rate component (adjusts every 6 months)
`purchaseLimit`	number	`10000`	Annual electronic purchase limit per person in dollars
`eeBonds`	object	`{...}`
`currentRate`	number	`2.7`
`guaranteedDoubling`	string	`"20 years (guaranteed to double in value)"`
`purchaseLimit`	number	`10000`	Annual electronic purchase limit per person in dollars
`recommendation`	string	`"I Bonds"`
`recommendationReason`	string	`"I Bonds currently offer 5.27% vs EE Bonds at 2.70%"`
`nextRateChange`	string	`"2024-05-01"`	Date of next scheduled I-Bond rate announcement
`lastUpdated`	string	`"2024-02-01T00:00:00.000Z"`	ISO 8601 timestamp of last data refresh

Errors

Read the HTTP status first, then error for the specific reason. The body names the parameter that has to change. Error handling covers the full status list and which of them are worth retrying.

Status	Meaning	What to do
`400`	Input was rejected	Read `error`; it names the parameter.
`401`	Key missing or invalid	Check the header name and the key value.
`403`	Key valid, but not permitted	A key restriction or IP allow-list; see key scoping.
`429`	Rate limited, or out of credits	Read `error` to tell them apart; see rate limits.

Use cases

Investment Research: Track I-Bond rates to optimize purchase timing around rate changes
Financial Planning: Factor I-Bond rates into inflation-protected savings strategies
Rate Tracking: Monitor I-Bond composite, fixed, and inflation rate components over time
Historical Analysis: Analyze historical I-Bond rates back to 1998 for trend research

Other ways to use I-Bond Rates

Set up I-Bond Rates on APIVerve, or reach the same source a different way. Your APIVerve account and credits work on all of them — one key, one balance.

Give it to an AI agentConnect over MCP and your agent calls it as a native tool — Claude, Cursor, ChatGPT.VerveKit →Reference →

Use it in Google Sheets or ExcelA =VERVE() formula fills a column — no script, no export, recalculates in place.VerveSheets →Reference →

Ground an agent on itA cited, machine-checkable fact your model can't produce on its own.VerveContext →Reference →

I-Bond Rates