Reverse-charge B2B sales with a checked VAT number

How to do it

Ask for the VAT number at checkout. Check it with the European Commission's VIES service, through its REST API or your tax service. Send your own VAT number with the request to get a consultation number, and store it with the date. If VIES is down, charge VAT or hold the order, then check again. Sales to businesses in your own country still carry VAT.

Example

async function checkVatNumber(countryCode, vatNumber) {
  const response = await fetch('https://ec.europa.eu/taxation_customs/vies/rest-api/check-vat-number', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ countryCode, vatNumber, requesterMemberStateCode: 'SE', requesterNumber: '556677889901' }),
    signal: AbortSignal.timeout(10_000),
  })
  if (!response.ok) throw new Error(`VIES answered ${response.status}`)
  const result = await response.json()
  return { valid: result.valid, consultationNumber: result.requestIdentifier, checkedAt: new Date().toISOString() }
}

import requests
from datetime import datetime, timezone

def check_vat_number(country_code: str, vat_number: str) -> dict:
    response = requests.post(
        "https://ec.europa.eu/taxation_customs/vies/rest-api/check-vat-number",
        json={"countryCode": country_code, "vatNumber": vat_number,
              "requesterMemberStateCode": "SE", "requesterNumber": "556677889901"},
        timeout=10,
    )
    response.raise_for_status()
    result = response.json()
    return {"valid": result["valid"], "consultation_number": result.get("requestIdentifier"),
            "checked_at": datetime.now(timezone.utc).isoformat()}

How to check

A checkout test with an invalid VAT number charges VAT. A valid number from another EU country gives zero VAT, a stored consultation number and the reverse charge note on the invoice.