U.S. Department of the Treasury Exchange Rate API — ustreasury-exchange-rate

Official U.S. Department of the Treasury (the United States) quarterly exchange rates for Node.js and TypeScript. The published tax authority rates behind tax filings, customs valuations, audits, and compliant invoicing — not market estimates, but the numbers U.S. Department of the Treasury itself prints, every quarter.

🚀 Why this client?

• 🏛️ Official published rates — U.S. Department of the Treasury's own table, with the publisher's own rate_date on every response
• 📅 History back to 2001 — point-in-time tables and daily series for any past date
• 🔀 Published vs derived, always flagged — computed inverse/cross pairs carry derived: true, never mixed with official prints
• ⚡ Zero dependencies — pure ESM + CJS over global fetch; Node 18+, Bun, Deno, and edge runtimes
• 🔷 Type-safe — full TypeScript definitions shipped with the package
• 🧾 Compliance-grade metadata — rate_type, publication date, and source disclaimer on every response

Official rate, not mid-market: every value here is a number U.S. Department of the Treasury itself published, fixed once printed and carrying the tax authority's own rate_date — what filings and audits require. Need the live interbank midpoint for pricing or display instead? Use the mid-market API or @allratestoday/sdk. The two can diverge by several percent.

🔑 Get your API key

Get a free API key at allratestoday.com/register — no credit card required. Latest rates are on every plan, including free.

📦 Installation

npm install ustreasury-exchange-rate

yarn add ustreasury-exchange-rate

pnpm add ustreasury-exchange-rate

Also published under the org scope as @allratestoday/ustreasury-exchange-rate — same code, same versions.

🏁 Quick start

import { getRate } from 'ustreasury-exchange-rate';

const pair = await getRate('USD', 'EUR', { apiKey: 'art_live_...' });
console.log(pair.rate, pair.rate_date); // the official U.S. Department of the Treasury rate, on the tax authority's own date

📚 API reference

• Latest pair rate — one pair from the latest published table
• Full published table — everything the tax authority printed, in one call
• Table for a date — the official table for an invoice or filing date
• Daily time series — one pair across a date range

Latest pair rate

Free plan and up. Pairs the tax authority does not print directly are resolved from its table and flagged (see Published vs derived rates below).

const pair = await getRate('USD', 'EUR', { apiKey: 'art_live_...' });

Response:

{
  bank: 'ustreasury',
  name: 'U.S. Department of the Treasury',
  rate_date: '2026-06-30',   // U.S. Department of the Treasury's own publication date
  source: 'USD',
  target: 'EUR',
  rate: 0.877,
  rate_type: 'quarterly',
  derived: false,
  method: 'published',
  disclaimer: '…'
}

Full published table

Free plan and up. The complete table for the latest publication date.

import { getLatestRates } from 'ustreasury-exchange-rate';

const table = await getLatestRates({ apiKey: 'art_live_...' });
console.log(table.rate_date, table.rates.length);

Response:

{
  bank: 'ustreasury',
  name: 'U.S. Department of the Treasury',
  rate_date: '2026-06-30',
  rates: [
    { "base": "USD", "quote": "EUR", "type": "quarterly", "value": 0.877 },
    // … the rest of the published table (145 currencies vs USD)
  ],
  disclaimer: '…'
}

Table for a date

Paid plans. The official table for any date since 2001 — weekends and holidays return the most recent published date, flagged via published_on_requested_date, which is exactly the in-force rate a filing needs.

import { getRatesForDate } from 'ustreasury-exchange-rate';

const day = await getRatesForDate('2026-06-30', { apiKey: 'art_live_...' });
// Optionally narrow to one pair:
const one = await getRatesForDate('2026-06-30', { apiKey: 'art_live_...', source: 'USD', target: 'EUR' });

Response:

{
  bank: 'ustreasury',
  requested_date: '2026-06-30',
  rate_date: '2026-06-30',                // the date actually published
  published_on_requested_date: true,      // false when a weekend/holiday fell back
  rates: [ /* the full table for that date */ ],
  disclaimer: '…'
}

Daily time series

Paid plans. One resolved rate per publication date — ready for charting, revaluation runs, or audit workpapers.

import { getHistory } from 'ustreasury-exchange-rate';

const series = await getHistory(
  { source: 'USD', target: 'EUR', from: '2026-01-01', to: '2026-06-30' },
  { apiKey: 'art_live_...' }
);

Response:

{
  bank: 'ustreasury',
  source: 'USD',
  target: 'EUR',
  from: '2026-01-01',
  to: '2026-06-30',
  count: 152,
  rates: [
    // one entry per publication date
    { date: '2026-06-30', rate: 0.877, rate_type: 'quarterly', derived: false, method: 'published' },
    // …
  ],
  disclaimer: '…'
}

Pass { symbol: 'EUR' } instead of source/target to get the raw published rows for one currency (all rate types, no pair resolution).

🗺️ Currencies covered

U.S. Department of the Treasury currently publishes rates covering 146 currencies (as of the latest table):

AED · AFN · ALL · AMD · AOA · ARS · AUD · AZN · BAM · BBD · BDT · BGN · BHD · BIF · BMD · BND · BOB · BRL · BSD · BWP · BYN · BZD · CAD · CDF · CHF · CLP · CNY · COP · CRC · CUC · CUP · CVE · CZK · DJF · DKK · DOP · DZD · EGP · ERN · ETB · EUR · FJD · GBP · GEL · GHS · GMD · GNF · GTQ · GYD · HKD · HNL · HTG · HUF · IDR · ILS · INR · IQD · IRR · ISK · JMD · JOD · JPY · KES · KGS · KHR · KMF · KRW · KWD · KYD · KZT · LAK · LBP · LKR · LRD · LSL · LYD · MAD · MDL · MGA · MKD · MMK · MNT · MRU · MUR · MVR · MWK · MXN · MYR · MZN · NAD · NGN · NIO · NOK · NPR · NZD · OMR · PEN · PGK · PHP · PKR · PLN · PYG · QAR · RON · RSD · RUB · RWF · SAR · SBD · SCR · SDG · SEK · SGD · SLE · SOS · SRD · SSP · STN · SYP · SZL · THB · TJS · TMT · TND · TOP · TRY · TTD · TWD · TZS · UAH · UGX · USD · UYU · UZS · VES · VND · VUV · WST · XAF · XCD · XCG · XOF · YER · ZAR · ZMW · ZWG

⚖️ Published vs derived rates

If U.S. Department of the Treasury does not print a pair directly, the API resolves it from the tax authority's own table and says so — official and computed values are never confused:

| method | derived | Meaning | | --- | --- | --- | | published | false | The tax authority printed this pair directly | | inverse | true | Computed as 1 ÷ the published opposite direction | | cross | true | Computed via USD from two published rates |

🛡️ Error handling

Errors are thrown as Error with status (HTTP code) and body (the API's JSON error) attached:

try {
  const pair = await getRate('USD', 'XXX', { apiKey: 'art_live_...' });
} catch (err) {
  console.log(err.message); // human-readable reason
  console.log(err.status);  // e.g. 404
}

| Status | Meaning | | ------ | ------- | | — | Missing apiKey (thrown before any request) | | 400 | Malformed date or parameters | | 401 | Invalid API key | | 403 | Endpoint needs a paid plan (historical dates & series) | | 404 | Pair or date range not covered by U.S. Department of the Treasury | | 429 | Monthly quota exceeded |

🔷 TypeScript

Full definitions ship with the package — no @types install:

import type { LatestRates, PairRate, DatedRates, RateEntry, HistoryQuery, RequestOptions } from 'ustreasury-exchange-rate';

📦 CommonJS

const { getRate } = require('ustreasury-exchange-rate');

getRate('USD', 'EUR', { apiKey: 'art_live_...' }).then((pair) => console.log(pair.rate));

💡 Quota tips

• Rates change once a quarter — cache the published table locally and a small monthly quota goes a long way.
• Every request counts toward your AllRatesToday quota, shared across all AllRatesToday endpoints on your key.

📖 Methods reference

| Method | Plan | Description | | ------ | ---- | ----------- | | getRate(source, target, { apiKey }) | Free | Latest rate for one pair, resolved from the published table | | getLatestRates({ apiKey }) | Free | The tax authority's full latest published table | | getRatesForDate(date, { apiKey, source?, target? }) | Paid | The official table (or one pair) for a YYYY-MM-DD date | | getHistory({ symbol \| source+target, from?, to? }, { apiKey }) | Paid | Daily series since 2001 |

🔗 Links

• U.S. Department of the Treasury rates page — live table, publication cadence, FAQ
• All tax authority sources
• API documentation · Interactive reference
• Register (free) · Pricing
• GitHub

📜 License

MIT