Learn / updated 2026-10-03

How EU VAT number validation works (VIES explained)

Selling business-to-business across EU borders usually requires checking that the customer's VAT number is valid. The European Commission runs VIES (the VAT Information Exchange System), which asks the tax authority of the customer's member state whether a VAT number is registered for cross-border trade.

Two kinds of check

Format check: does the number have the right length and pattern for its country? This is instant and offline, but it only catches typos.
VIES check: is the number registered, according to the member state's own database? This needs a live call and can return the registered name and address where the member state provides them.

Country prefixes

A VAT number starts with a two-letter country prefix. Most prefixes match the ISO country code, but Greece uses EL and Northern Ireland uses XI for goods. Always send the prefix with the number.

What the answer means

A valid answer says the number is registered for VAT in that member state at the time of the check. It is not a legal confirmation for your own tax records: if you need official proof for a specific transaction, use the member state's own confirmation procedure.

Why a check can be slow or fail

VIES queries national databases, and some of them are temporarily unavailable or limit concurrent requests. Good tooling retries transient errors, and an "unavailable" answer is different from "invalid": it means the question could not be answered, not that the number is wrong. Ambolt's check retries transient errors and does not charge when the source cannot answer.

Frequently asked questions

Does a valid number mean the company is trustworthy? No. It means the number is registered. It says nothing about the company's finances.

Can I check my own number? Yes, the check works for any registered number.

Does the result include the company name? Where the member state shares it. Some countries return only valid or invalid.

Try the free EU VAT number check or read the API reference. Not tax advice.

Informational only, not financial, legal or tax advice.