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Go EU VAT Validation API

Validate EU VAT numbers from Go backends using only the standard library. Returns VIES registration status, company name, and address in a single REST call — no SOAP, no XML, no external packages required.

Quick start

curl -H "Authorization: Bearer YOUR_API_KEY" \
  http://localhost:3000/api/v1/validate/DE/DE123456789

Code example

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

package main

import (
  "encoding/json"
  "fmt"
  "net/http"
  "os"
)

func validateVAT(country, vatNumber string) (map[string]any, error) {
  url := fmt.Sprintf("http://localhost:3000/api/v1/validate/%s/%s", country, vatNumber)
  req, _ := http.NewRequest("GET", url, nil)
  req.Header.Set("Authorization", "Bearer "+os.Getenv("TAXID_API_KEY"))

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

  var result map[string]any
  json.NewDecoder(resp.Body).Decode(&result)
  return result, nil
}

func main() {
  result, _ := validateVAT("DE", "DE123456789")

  if result["valid"] == true {
    fmt.Println("Valid EU business:", result["company_name"])
  } else if result["status"] == "service_unavailable" {
    fmt.Println("VIES unavailable — retry later")
  } else {
    fmt.Println("Invalid VAT number")
  }
}

curl "http://localhost:3000/api/v1/validate/DE/DE123456789" \
  -H "Authorization: Bearer $TAXID_API_KEY"

# {
#   "valid": true,
#   "status": "active",
#   "company_name": "Example GmbH",
#   "company_address": "Musterstraße 1, 10115 Berlin",
#   "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. Store your API key as an environment variable (export TAXID_API_KEY=your_key) and read it with os.Getenv(). Never hardcode credentials in source files.

2. 2

   Make a GET request with net/http

   Create an http.Request with http.NewRequest("GET", url, nil), set the Authorization header, and call http.DefaultClient.Do(req). This uses only the Go standard library — no external packages or go get required.

3. 3

   Decode the JSON response

   Use json.NewDecoder(resp.Body).Decode(&result) to parse the response into a map[string]any or a typed struct. Check result["valid"] == true for an active EU business, and result["status"] for the detailed outcome ('active', 'invalid', 'not_found', 'service_unavailable').

4. 4

   Handle service_unavailable and implement retries

   VIES has occasional downtime. When status is 'service_unavailable', return a distinct error type from your validate function so callers can handle it differently from an invalid VAT number. Implement exponential backoff with a maximum of 3 retries for transient errors.

Frequently asked questions

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