Clients and address book · 3 min read

Checking a foreign client's tax ID through VIES

How to verify a foreign client's tax ID through the EU's VIES system, how the app saves the result with a date, and how to filter your foreign clients.

What VIES is

VIES (VAT Information Exchange System) is the European Union's system for checking whether the tax ID (DIČ) of a business from an EU member state is valid. It's run by the European Commission and is publicly available at ec.europa.eu/taxation_customs/vies.

VIES links the national VAT registers of every EU country and lets you check, in real time, whether a given tax ID is valid and who it belongs to.

When to use VIES

Checking through VIES matters when you're invoicing a foreign client from the EU who is a VAT payer in their own country. Correctly verifying the tax ID is key to applying reverse charge — that is, issuing an invoice without Czech VAT.

The conditions for invoicing without Czech VAT differ depending on what you're supplying.

A service to a business in the EU (the place of supply follows the customer's registered seat, § 9 odst. 1 ZDPH):

  • The customer is a business registered for VAT in another EU member state.
  • The supplier can be either a VAT payer or a non-payer — being a VAT payer isn't a condition here. A non-payer does become an identified person by supplying such a service and has to register within 15 days; even an identified person invoices without Czech VAT.

Goods delivered to a business in the EU (exempt under § 64 ZDPH):

  • You are a VAT payer in the Czech Republic — the exemption only applies to VAT payers.
  • The customer has given you the tax ID under which they're registered for VAT in another member state.
  • The goods are actually dispatched or transported from the Czech Republic to another member state.
  • You report the supply in the EC Sales List.

How to verify a tax ID in Taxorio

The check runs automatically, right in the client form. As soon as you enter a foreign EU number into the tax ID (DIČ) field (e.g. SK2020317068, DE…), Taxorio verifies it against VIES in the background and shows the result right under the field:

  1. Open Clients → New client (or edit an existing one) and pick the client's country from the list — the app offers the full list of countries, not just EU ones.
  2. Enter the EU tax ID into the tax ID (DIČ) field, including the country prefix (SK, DE, AT…).
  3. Underneath the field you'll see an informational status: Valid EU VAT payer in VIES (including the company name from the register), or a warning that the tax ID isn't valid.

When you save the client, Taxorio saves the result of the check to the client, along with the date, and shows it on the client's card. For a successful check, it's the day VIES actually answered — the result may come from an earlier check of the same tax ID, at most 7 days old. If the tax ID doesn't change, saving the client doesn't repeat the check.

The Verify again button next to the tax ID field always asks VIES anew. If the tax ID is already saved on the client, it saves the new result and date straight away; a tax ID you're still typing is saved together with the client. If VIES isn't responding at the moment, the earlier result stays.

When you issue an invoice or a proforma invoice to the EU (a service or goods for a business in the EU), the app asks VIES anew by itself and saves the result with the date of the check on the document — so you don't have to verify by hand before every invoice. A final invoice, a credit note and a tax document for a received payment take over the check from the original document. If VIES doesn't answer within a few seconds, the document is issued anyway and the app warns you that the check didn't go through.

The record in Taxorio is not an official confirmation, though. You get proof for a tax audit directly on the VIES website: if you also enter your own tax ID that is valid in VIES (VAT payers and identified persons have one), VIES issues a consultation number that proves when, and with what result, you checked the tax ID. Without your own tax ID, keep at least the result of the check, e.g. a screenshot.

The check is informational — even an invalid or temporarily unverified tax ID doesn't stop you from saving the client and moving on. A Czech tax ID isn't checked through VIES; those details are filled in from ARES instead.

You can request the same check through the AI assistant (by asking "Verify tax ID …") and, from external AI tools, through the MCP integration (PRO plan).

Checking that the country matches the tax ID

The app checks that the tax ID's prefix matches the client's selected country (e.g. a tax ID starting with SK for a client whose country is set to Slovakia). It flags any mismatch in the client list with a warning icon. When you edit the client, it offers a one-click fix under the Country field — the "Set [country from the tax ID]" button switches the country straight away.

What the check results mean

  • Valid tax ID — the tax ID exists and is active. The client is a registered VAT payer in that EU country. You can issue the invoice without Czech VAT.
  • Invalid tax ID — the tax ID doesn't exist in the database, or it's been cancelled. Contact the client before issuing the invoice and ask for a current tax ID.
  • Can't be verified — the national register of that country is temporarily unavailable. Try the check again in a few minutes with the "Verify again" button, or check directly on the VIES website.
⚠️ Note: An invalid or unverified tax ID doesn't automatically mean you can't invoice. Without a valid customer tax ID, though, an invoice to the EU without Czech VAT is hard to defend — a VAT payer then invoices with Czech VAT, a non-payer or an identified person as an ordinary domestic supply. If in doubt, consult a tax advisor. The app won't issue a supply of goods to the EU at all if VIES marks the tax ID as invalid at issue. For a service, or when VIES is unavailable, it issues the document but warns you; VAT payers and identified persons also see such an invoice separately in the Taxes & insurance → VAT section.
💡 Tip: In the client list, filter foreign clients with the Foreign toggle — it shows everyone whose country is set outside the Czech Republic, or who has a foreign tax ID. We recommend verifying a new foreign client's tax ID before the first invoice, and keeping the confirmation from the VIES website (with a consultation number, if you have your own tax ID) in case of a tax audit.