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How to prove you checked a customer’s VAT number

Updated 2026-10-11

If you sell to businesses in other EU countries without charging VAT (the reverse charge, or a zero-rated intra-community supply of goods), you're expected to check that your customer's VAT number is valid. The problem: a screenshot of a "valid" result is weak evidence. The VIES consultation number is the strong version.

What is a consultation number?

When you run a VIES check and also supply your own VAT number as the "requester", VIES returns a unique identifier, the consultation number (e.g. WAPIAAAAZ…). It records that you (the requester) checked this VAT number at this moment, and what the result was. Tax authorities in several member states accept it as proof of due diligence, and they can look it up on their side.

Why it matters

Intra-community supplies of goods: since the 2020 "quick fixes", a valid VAT number of the customer, registered in VIES, is a substantive condition for the VAT exemption. If the customer's number turns out to be invalid, you may owe the VAT yourself.
B2B services: the reverse charge depends on the customer being a taxable business. A valid VAT number is the standard evidence.
Audits: tax audits happen years after the transaction. "We checked it at the time" is only convincing if you can show a dated, verifiable record.

How to get a consultation number

Run the VIES check with your own valid EU VAT number filled in as the requester.
If both numbers are valid, VIES returns a consultation number along with the result.
Store it with the date, the checked number and the result, ideally linked to the invoice.

Note: if your own number is wrong, VIES returns INVALID_REQUESTER_INFO and no consultation number. Germany also offers its own "qualified confirmation" through the BZSt for German businesses; the consultation number is the EU-wide equivalent.

How often should you check?

Check at onboarding and again periodically. VAT numbers get deregistered, and a number that was valid last year may not be valid today. Many businesses re-check their whole customer list quarterly, before filing their EC Sales List / recapitulative statement.

Doing this at scale

Checking dozens or thousands of customers one by one in the VIES web form is painful. With VATcheckly Pro you upload a CSV, set your own VAT number once, and get every result back with its consultation number, plus a printable proof record per check for your audit file.

This guide is general information, not tax advice. Rules differ between member states; ask your tax adviser about your situation.

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