Free Income Tax API — 1,000 Requests/Month, No Credit Card

What you get on the free tier

The free tier gives you everything you need to fully evaluate the API and build a working prototype. 1,000 requests/month is enough to handle hundreds of user sessions per month, or tens of thousands if you implement basic caching (which you should).

What the free tier includes:

• All 111 countries — the same data that paid plans access
• Full response detail — complete breakdown including deductions, brackets applied, social contributions, effective rate, net income, and monthly equivalent
• Currency conversion — pass any ISO 4217 currency code and the API converts the income before calculating
• Rate limit headers — X-RateLimit-Remaining and X-RateLimit-Used on every response so you can monitor usage
• Hard monthly cap — no surprise bills; you simply get a 429 when the limit is reached

What requires a paid plan:

• Country detail and raw rates endpoints (/countries/{country_code}, /countries/{country_code}/rates) — Starter+
• Historical tax year data — Growth+
• Bulk summary ranking across all 111 countries (/summary) — Growth+
• Multi-country comparison in a single call (/compare) — Pro+

Getting your free API key

Free keys are provisioned manually. To request yours:

1. Email daniel@countrytaxcalc.com with the subject line "API Access - Free Tier"
2. Include a brief note about what you're building — this helps prioritise support if you have questions
3. You'll receive your API key by reply email, typically within a few hours during UK business hours

The key is a long random string — keep it private. Do not commit it to GitHub, hardcode it in client-side JavaScript, or share it publicly. If you accidentally expose it, contact us immediately to rotate it.

Your first API call

Once you have your key, here's the fastest path to a working response. The example below calculates UK income tax for a £50,000 gross salary.

cURL

curl -X POST https://api.countrytaxcalc.com/api/v1/calculate \
  -H "Content-Type: application/json" \
  -H "X-API-Key: your_api_key_here" \
  -d '{
    "income": 50000,
    "currency": "GBP",
    "country": "GB"
  }'

Python

import requests

response = requests.post(
    "https://api.countrytaxcalc.com/api/v1/calculate",
    headers={
        "Content-Type": "application/json",
        "X-API-Key": "your_api_key_here"
    },
    json={
        "income": 50000,
        "currency": "GBP",
        "country": "GB"
    }
)

data = response.json()
print(f"Net income: £{data['totals']['net_income']:,.2f}")
print(f"Effective rate: {data['totals']['effective_tax_rate']}%")

JavaScript (Node.js)

const response = await fetch(
  "https://api.countrytaxcalc.com/api/v1/calculate",
  {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "X-API-Key": process.env.COUNTRYTAXCALC_API_KEY  // server-side only
    },
    body: JSON.stringify({
      income: 50000,
      currency: "GBP",
      country: "GB"
    })
  }
);

const data = await response.json();
console.log(`Net income: £${data.totals.net_income.toLocaleString()}`);
console.log(`Effective rate: ${data.totals.effective_tax_rate}%`);

What the response looks like

{
  "country": "United Kingdom",
  "country_code": "GB",
  "tax_year": 2026,
  "currency": "GBP",
  "currency_symbol": "£",
  "gross_income": 50000,
  "breakdown": {
    "deductions": [
      { "name": "Personal Allowance", "amount": 12570 }
    ],
    "taxable_income": 37430,
    "national_income_tax": {
      "amount": 7486,
      "effective_rate": 0.1497,
      "marginal_rate": 0.20,
      "brackets_applied": [
        { "threshold": 0, "rate": 0.20, "tax": 7486 }
      ]
    },
    "social_contributions": [
      {
        "name": "National Insurance",
        "type": "social_security",
        "amount": 2984,
        "rate": 0.08,
        "capped": false
      }
    ]
  },
  "totals": {
    "total_deductions": 12570,
    "total_tax": 10470,
    "net_income": 39530,
    "effective_tax_rate": 20.94,
    "take_home_percentage": 79.06,
    "monthly_net_income": 3294.17
  },
  "metadata": {
    "calculation_date": "2026-07-08T10:00:00.000Z",
    "data_source": "HMRC",
    "last_updated": "2026-04-06",
    "accuracy_confidence": 0.95
  }
}

Monitoring your usage

Every response includes rate limit headers. Read them to keep track of how much of your free allocation you've used:

# Response headers
X-RateLimit-Limit: 1000
X-RateLimit-Used: 47
X-RateLimit-Remaining: 953
X-RateLimit-Reset: 1754006400   # Unix timestamp: 1 Aug 2026 00:00 UTC

Free tier endpoint reference

On the free tier, two endpoints are available:

POST /api/v1/calculate Free

Full tax calculation for a specific income and country. Supports all 111 countries, optional jurisdiction (US states, Canadian provinces), and optional currency conversion.

Required fields: income (positive number), country (country name or ISO code)

Optional fields: currency (ISO 4217), jurisdiction (state/province code), tax_year (Growth+ only)

GET /api/v1/countries Free (no key needed)

Returns the list of all 111 supported countries with their codes, currencies, and whether they have sub-jurisdictions. This endpoint is publicly accessible — no API key required — useful for populating your country selector.

curl https://api.countrytaxcalc.com/api/v1/countries

What to build with a free API key

1,000 requests/month is more than enough for:

• A salary comparison tool — if you cache per country+income combination, 1,000 unique requests covers a huge range of combinations
• A job listing page — show after-tax salary for each country where a role is available
• A relocation calculator — let users compare their current country against a few target destinations
• An offer letter generator — calculate net income for a candidate's location before sending
• Internal HR tooling — a spreadsheet or internal dashboard to compare compensation packages

When to upgrade from the free tier

The free tier is intentionally generous for development and low-traffic use. Here's when to consider a paid plan:

All paid plans include a 7-day money-back guarantee. See the pricing page for full plan details.