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ERP supplier VAT number validation

Validate supplier VAT numbers in SAP, NetSuite, or Xero during onboarding. Prevent invalid numbers from entering your accounting system and causing rejected invoices.

Implementation steps

1. 1

   Trigger on new supplier creation

   Register a webhook or server-side script that fires when a new vendor record is saved in your ERP. In SAP, implement a BAdI on the VENDOR_ADD_DATA enhancement spot; in NetSuite, use a beforeSubmit User Event script on the Vendor record type; in Xero, subscribe to the contacts.created webhook via the Xero API. Pass the supplier's country code and VAT number extracted from the vendor form to your validation service.

2. 2

   Validate VAT via webhook or batch

   Call GET /api/v1/validate/:country/:vat from your middleware and inspect the status field. For real-time hooks, respond synchronously to the ERP with the result so the save can be blocked or warned inline. For batch jobs, process up to 10 concurrent requests at a time and implement exponential backoff for 429 rate-limit responses; TaxID caches active numbers for 24 hours so previously validated numbers return in under 10 ms.

3. 3

   Update supplier record with validation status

   Write the status, company_name, company_address, request_id, and validated_at back to the ERP vendor record using custom fields. Storing the company_name alongside the validation result lets AP staff cross-check that the name on an incoming invoice matches the VIES-confirmed entity name, catching cases where a supplier has restructured and their invoices now reference a different legal entity.

4. 4

   Flag mismatches for manual review

   Set the ERP vendor record to a 'hold' payment status when status is 'invalid' or when the company_name from VIES does not match the name on file. Route a task to the AP team's review queue with the TaxID request_id as a reference. This ensures that an invalid number never silently passes through to a posted invoice, which would require a manual VAT correction with your tax authority.

Code example

const res = await fetch(
  'http://localhost:3000/api/v1/validate/DE/DE123456789',
  { headers: { 'Authorization': 'Bearer YOUR_API_KEY' } }
);
const { valid, status, company_name, company_address } = await res.json();

if (valid) {
  console.log(`Valid EU business: ${company_name}`);
} else if (status === 'service_unavailable') {
  // VIES is temporarily down — retry or allow with manual check
  console.log('VIES unavailable — check back in a few minutes');
} else {
  console.log('Invalid VAT number — charge local tax rate');
}

import requests

res = requests.get(
    "http://localhost:3000/api/v1/validate/DE/DE123456789",
    headers={"Authorization": "Bearer YOUR_API_KEY"}
)
data = res.json()

if data["valid"]:
    print(f"Valid: {data['company_name']}")
elif data["status"] == "service_unavailable":
    print("VIES temporarily unavailable")
else:
    print("Invalid VAT number")

API response

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

{
  "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.

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