VIES Consultation Number and VAT Audit Trail for EU Compliance

When auditors examine your EU B2B invoices, they ask one question: how do you know your customer was VAT-registered at the time you issued the invoice? The VIES consultation number is the answer. Here is what it is, why it matters, and what your application needs to store.

The compliance problem: proof of VAT status at invoice time

Selling B2B across EU member states usually means issuing invoices under the reverse charge mechanism — the seller charges zero VAT and the buyer self-assesses at their local rate. The condition for doing this correctly is that the buyer holds a valid, active VAT number at the moment the invoice is issued.

That check is not a one-time event. A VAT registration that was valid last year may have lapsed. A company that merged, restructured, or deregistered will no longer appear in the EU-27 registry. The obligation sits with the seller: if you apply zero-rating and the buyer's VAT status cannot be demonstrated, the tax liability can fall back to you.

Tax authorities — particularly in Germany and France — increasingly ask for documentary evidence that a VAT status check took place. A printed screenshot from a browser session is not sufficient for this. What they expect is a timestamped, system-generated record that ties a specific VAT number, a specific timestamp, and a specific outcome together. The VIES consultation number is that record, issued by the European Commission itself.

If you are building the integration from scratch, see the guide on how to validate EU VAT numbers programmatically for the full technical walkthrough.

What is the VIES consultation number?

VIES (VAT Information Exchange System) is the European Commission's central registry for EU VAT numbers. When you query it using the checkVatApprox operation — which requires you to supply your own VAT number as the requester — the Commission issues a consultation number: a unique reference string that permanently records the fact that a specific VAT number was checked, at a specific time, by a specific requester.

It looks like this: WAPIAAAAWpgnLGnO. It is not the VAT number itself — it is a receipt for the lookup, analogous to a transaction reference number. The EU Commission can cross-reference it if a tax authority enquires.

This is different from storing the VAT number in your database. Any system could store a string. The consultation number proves that a live query was sent to the official EU source and that it returned a result — with your identity as the requester on record.

Quick Fixes 2020 — why the check is now a substantive condition

Before January 2020, having a customer's VAT number was treated in many member states as an administrative formality — useful but not strictly required for zero-rating. Council Directive 2018/1910 (the Quick Fixes package, transposed January 2020) changed this for intra-EU supplies of goods: a valid VAT number registered in the EU-27 is now a substantive legal condition for zero-rating, not merely an evidentiary one.

For cross-border B2B services, the buyer's VAT number determines whether the reverse charge applies under the general B2B place-of-supply rule. The substantive-condition framing from Quick Fixes applies to goods specifically, but the practical implication for services is the same: you need to be able to show that you confirmed VAT status at the time of invoicing.

What the consultation number does is put you in the strongest defensible position: you can show an auditor the reference number, the timestamp, and the VAT number that was checked, and they can verify it against the EU Commission's own records.

What vatnode returns in the API response

Every vatnode validation response includes the fields needed to build a complete audit record. See the API reference for the full response schema. The fields relevant to audit are:

Example response with a consultation number present:

{
  "valid": true,
  "vatId": "DE134214316",
  "countryCode": "DE",
  "countryName": "Germany",
  "companyName": "EXAMPLE GMBH",
  "companyAddress": "MUSTERSTRASSE 1, 10115 BERLIN",
  "checkId": "01956b4a-1234-7abc-8def-0123456789ab",
  "verifiedAt": "2026-04-23T09:14:52.301Z",
  "consultationNumber": "WAPIAAAAWpgnLGnO"
}

How to configure your requester VAT number

The VIES system issues a consultation number only when the query includes a requester VAT number — that is, your own EU VAT number identifying who is making the check. Without it, VIES validates the VAT status but does not issue an audit reference.

There are two ways to supply this to vatnode:

• Dashboard (recommended):Go to Settings → Requester VAT and enter your EU VAT number. vatnode will include it on every live VIES query automatically. No changes to your integration code are required.
• Per-request query parameters: Pass requesterCountryCode and requesterVatNumber on the request URL. Useful for multi-entity setups where the requester varies by transaction.

# Without requester VAT: consultationNumber will be null
curl https://api.vatnode.dev/v1/vat/DE134214316 \
  -H "Authorization: Bearer vat_live_your_key_here"

# With requester VAT: consultationNumber is returned
curl "https://api.vatnode.dev/v1/vat/DE134214316?requesterCountryCode=IE&requesterVatNumber=6388047V" \
  -H "Authorization: Bearer vat_live_your_key_here"

What to store alongside your invoices

For every B2B invoice issued with reverse charge applied, persist the following fields from the vatnode response in your invoice or order record. Audit trail storage is available on all plans, and check records are accessible through the dashboard and API.

{
  "invoiceId":          "inv_2024_001",
  "vatNumber":          "IE6388047V",
  "consultationNumber": "WAPIAAAAZ27qPadm",  // EU Commission audit token
  "validatedAt":        "2026-03-26T14:25:57.209Z",
  "countryCode":        "IE"
}

Here is a TypeScript example showing how to persist these fields at checkout:

interface VatAuditRecord {
  vatId: string
  consultationNumber: string | null
  checkId: string
  verifiedAt: string
  companyName: string | null
  companyAddress: string | null
}

async function validateAndStoreAuditRecord(
  invoiceId: string,
  buyerVatId: string
): Promise<{ applyReverseCharge: boolean; auditRecord: VatAuditRecord }> {
  const response = await fetch(
    `https://api.vatnode.dev/v1/vat/${encodeURIComponent(buyerVatId)}`,
    { headers: { Authorization: `Bearer ${process.env.VATNODE_API_KEY}` } }
  )

  if (!response.ok) {
    const err = await response.json()
    throw Object.assign(new Error(err.error.message), { code: err.error.code })
  }

  const result = await response.json()

  const auditRecord: VatAuditRecord = {
    vatId: result.vatId,
    consultationNumber: result.consultationNumber,  // EU Commission reference
    checkId: result.checkId,                        // vatnode check ID
    verifiedAt: result.verifiedAt,                  // ISO 8601 timestamp
    companyName: result.companyName,
    companyAddress: result.companyAddress,
  }

  // Persist alongside the invoice — do not discard these fields
  await db.invoices.update(invoiceId, {
    vatAuditRecord: auditRecord,
    applyReverseCharge: result.valid,
  })

  return { applyReverseCharge: result.valid, auditRecord }
}

Frequently asked questions