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Cloudflare Workers EU VAT Validation API

Validate EU VAT numbers at the edge with Cloudflare Workers and the TaxID API. Store your key as a Worker secret, proxy validation requests globally with sub-50ms latency, and cache valid results at the Cloudflare edge to cut repeat round-trips to VIES.

Quick start

curl -H "Authorization: Bearer YOUR_API_KEY" \
  https://www.taxid.dev/api/v1/validate/DE/DE123456789

Code example

Full integration example including error handling for service_unavailable responses from VIES.

// Store your API key as a Worker secret:
// $ wrangler secret put TAXID_API_KEY

export default {
  async fetch(request, env) {
    const { searchParams } = new URL(request.url);
    const country = searchParams.get('country');
    const vat     = searchParams.get('vat');

    if (!country || !vat) {
      return Response.json({ error: 'country and vat required' }, { status: 400 });
    }

    const res = await fetch(
      `https://www.taxid.dev/api/v1/validate/${country}/${vat}`,
      { headers: { 'Authorization': `Bearer ${env.TAXID_API_KEY}` } }
    );

    const result = await res.json();

    // Cache valid results at the Cloudflare edge for 1 hour
    const ttl = result.valid ? 3600 : 0;
    return Response.json(result, {
      headers: { 'Cache-Control': ttl ? `max-age=${ttl}` : 'no-store' }
    });
  }
};

# Test locally with wrangler:
# wrangler dev — then curl "http://localhost:8787?country=DE&vat=DE123456789"

# Or call the TaxID API directly:
curl "https://www.taxid.dev/api/v1/validate/DE/DE123456789" \
  -H "Authorization: Bearer $TAXID_API_KEY"

# {
#   "valid": true,
#   "status": "active",
#   "company_name": "Example GmbH",
#   "cached": false
# }

API response

The TaxID API returns a consistent JSON response for every validation:

{
  "valid": true,
  "status": "active",
  "country_code": "DE",
  "vat_number": "DE123456789",
  "company_name": "Example GmbH",
  "company_address": "Musterstraße 1, 10115 Berlin",
  "request_date": "2026-05-10T00:00:00.000Z",
  "cached": false,
  "request_id": "req_01j..."
}

Implementation steps

1. 1

   Get a free TaxID API key

   Sign up at taxid.dev/signup for a free key with 100 validations/month. Store it as a Worker secret with wrangler secret put TAXID_API_KEY so it is encrypted at rest and accessed through the env binding — never hard-coded in your Worker source or wrangler.toml.

2. 2

   Write the fetch handler

   In your Worker's fetch(request, env) handler, read the country and number from the request URL, then call https://www.taxid.dev/api/v1/validate/{country}/{vat} with an Authorization header built from env.TAXID_API_KEY. Return Response.json(result) so any origin app can consume it.

3. 3

   Cache valid results at the edge

   Use the Cache API or a Cache-Control header to store 'active' responses at the Cloudflare edge for up to an hour, and skip caching 'invalid' or 'service_unavailable' results. Edge caching means a repeat lookup for the same number is served from the nearest data center without touching VIES again.

4. 4

   Guard the endpoint

   Because a Worker is publicly reachable, add a shared-secret header check or Cloudflare Access in front of it so only your own apps can call it. This prevents third parties from burning your TaxID quota through your Worker.

5. 5

   Return structured results to callers

   Forward the valid, status, company_name, and company_address fields to the calling application, which decides whether to apply reverse-charge. Keep the tax-treatment decision in your origin app, not the Worker, so business logic stays in one place.

Frequently asked questions

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