Format errors (most common)
- Missing country prefix (e.g.,
DE, FR, ES). - Wrong prefix for the customer’s establishment country (prefix is part of the VAT ID).
- Extra spaces or punctuation copied from invoices/emails.
- Using a domestic tax number instead of the EU VAT identification number.
Member state service unavailable
- VIES depends on the national VAT database of each member state.
- If a member state endpoint is down, VIES may show an unavailability message even for otherwise valid numbers.
- Treat this as a temporary technical condition and capture evidence of the outage.
Timeouts and intermittent failures
- Retries can succeed minutes later due to load, maintenance, or routing issues.
- Use a single clean input (uppercase prefix, no spaces) for retries.
- If you automate checks, apply a short backoff and limit repeated queries.
Valid number but missing name/address
Some member states return only validity. Others may suppress details for specific entity types. This is a data-return policy issue, not necessarily a validity problem.
When to ask the customer for supporting proof
- Repeated ‘invalid’ results after format checks.
- Urgent shipment/invoicing where VAT treatment depends on validity.
- Discrepancy between VIES and customer-provided registration documents.
What to store for audit trails
- Query input, timestamp, output status, and any reference ID.
- Evidence of outages/unavailability when applicable.
- Customer-provided proof (certificate or official register extract) where used.
Related pages
VAT verification overview | VAT formats by country | When to use VAT vs EORI vs LEI
