You checked the VAT number. Now prove it

A year and a half ago you delivered to a customer in Germany. Zero rate, because it was an intra-Community supply, and you checked the VAT number neatly on a free verification page. Today the Tax Authorities ask for proof of that check. A screenshot you never took is no proof. In this article you will read why the VIES verification number is proof, and how you can check a VAT number for free from now on, complete with that piece of evidence.

No zero rate without proof

With an intra-Community supply, a sale to a VAT-liable customer in another EU member state, you may charge 0 percent VAT. There is a condition attached: you must be able to demonstrate that you have checked your customer's VAT number. If you cannot, the Tax Authorities can refuse the zero rate and levy 21 percent after all. Usually a fine and interest come on top of that.

The check itself runs through VIES, the system of the European Commission. VIES checks the number with the tax authority of the country that issued it, so a German number is checked in Germany. A saved VIES check counts as the proof the Tax Authorities want to see.

And that is exactly where it pinches. Most free verification pages only show "valid" or "invalid" on your screen. Close the tab, and there is nothing left to show that the check ever took place.

The verification number is your piece of evidence

When you query VIES, it issues a reference: the verification number. With it you can later trace that you checked precisely that number on that date. Not your own note, not a screenshot, but a reference from the system itself. We think that is the difference between a check and a defence.

AI VAT Number Validation, our free product, checks an EU VAT number through VIES with the tax authority of the issuing country and returns that verification number to you. You sign up with your e-mail address at mcp-vat.iwebdevelopment.com, connect the connection to an AI assistant that supports MCP (Model Context Protocol, the open standard that connects AI assistants to software), such as Claude or ChatGPT, and ask your question in plain language. You get 100 verifications per month per organisation, and no accounting package is needed.

This is what it looks like with our own number: NL855303943B01, valid, registered in the name of CODEX CONNECTORS B.V., address EMMASINGEL 00033 5611AZ EINDHOVEN, checked on 28 August 2026, verification number WAPIAAAAaBIWFlcX. That single line is exactly what you want to be able to show a year and a half from now.

One condition: enter your own VAT number as the applicant. Without your own number you will be told whether the number is valid, but you will not get a verification number.

"Valid" is not the same as "correct"

A valid VAT number proves that the number exists and is active. It does not prove that it belongs to your customer. That is why you can supply a company name and address with the check, which are tested against the registration. For a Dutch number the connector optionally adds the name and address automatically from the Trade Register, so that there is something to cross-check. That addition costs one search from the KVK credit and can be switched off.

Let's be honest: not every member state actually checks that data. The Netherlands, for example, does not verify company details during a VAT number check. The connector simply says so: name and city have not been checked. We would rather have that than pretend everything has been verified.

The same goes for outages. If VIES is overloaded or temporarily unreachable, you get "cannot be checked, try again shortly". Never "invalid". That difference is worth money, because an unjustified "invalid" means you refuse a customer or wrongly charge 21 percent. We saw it happen live during testing: VIES itself returned a busy notice, and the connector translated it into "the VAT check service is currently busy".

ViDA makes clean VAT numbers essential

Another reason to set this up properly now. From 1 July 2030, structured e-invoicing becomes mandatory for intra-EU B2B transactions, with digital reporting to the tax authorities that comes close to real time. That package is called ViDA, VAT in the Digital Age. The quality of the VAT numbers in your records shifts from tidy to essential, because a wrong number will no longer surface only during a later audit, but during the reporting itself. Anyone who now makes a habit of checking every number with supporting evidence will have no extra work left by then.

Also included in your accounting connector

If you already use Exact Online AI Connect, Twinfield AI Connect or AFAS AI Connect, the same feature is included for free as the "KVK and VAT verification" module. On by default, nothing to activate, with the same monthly credit: 100 VAT verifications, plus 50 searches and 25 profiles from the Trade Register, the features of our free KVK sister product. If you need more, switch on the "KVK and VAT verification extra" add-on: 10 euros per month, good for 1000 searches, 1000 VAT verifications and 100 profiles.

The difference with the free product is not in the volume, but in the location. The check runs inside your own ERP connector, so your assistant combines it right away with what is in your records, without a second connection. For example, in a single conversation you can look up a debtor's VAT number and have it checked. You can read more about that on the page of Exact Online AI Connect.

From now on, check with evidence

You already check a VAT number anyway. So do it in a way that actually helps you when the Tax Authority asks: with a verification number as supporting evidence and a cross-check that honestly says what it could not verify. The connector works alongside your records and changes nothing in them; it only reads. On top of that, iWebDevelopment is ISO 27001 certified and independently pentested. Signing up costs you an email address.

Want to try it yourself? Connect AI VAT Number Validation for free →