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EU VAT validation in Go

Validate EU VAT numbers in Go using the standard net/http package. No external dependencies required — works with any Go 1.18+ project, from simple CLIs to high-throughput microservices.

Implementation steps

  1. 1

    Import net/http and encoding/json from the standard library

  2. 2

    Build a GET request with the Authorization header

  3. 3

    Decode the JSON response into map[string]any or a typed struct

  4. 4

    Handle valid, invalid, and service_unavailable cases

Code example

Go

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

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 request:

200 OK (active)valid
{
  "valid": true,
  "status": "active",
  "country_code": "DE",
  "vat_number": "123456789",
  "company_name": "Example GmbH",
  "company_address": "Musterstraße 1, 10115 Berlin",
  "request_date": "2026-05-10T00:00:00.000Z",
  "cached": false,
  "request_id": "req_01j..."
}

Error handling

The API uses a consistent Stripe-style error format. Always handle service_unavailable separately — VIES has occasional downtime and you should not reject valid customers during outages.

active

VAT number is valid and the business is registered

invalid

VAT number format is wrong or not registered in VIES

service_unavailable

VIES or the national system is temporarily down — retry later

Evaluating EU VAT APIs? Compare TaxID vs Vatstack, Vatlayer, Avalara →

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