EU VAT Reverse Charge: What Developers Need to Know

For ordinary cross-border B2B SaaS services, reverse charge makes the customer responsible for accounting for VAT. The supplier invoices without charging VAT. This guide explains the conditions and shows how to collect registration evidence without turning a VAT lookup into a tax decision.

What is the reverse charge?

Reverse charge changes who accounts for VAT. It is different from a statutory zero rate and from the intra-Community goods exemption in Article 138 of the VAT Directive. The customer accounts for output VAT and may deduct input VAT to the extent permitted by the applicable deduction rules.

When does the reverse charge apply?

For the services covered here, Article 44 normally places the supply where the business customer is established, or at the fixed establishment receiving the service. Article 196 makes the customer liable when the supplier is not established in that EU Member State. The supplier can be in another EU country or outside the EU, including the US or UK. Both parties do not have to be established in different EU Member States.

Establish the customer's taxable-person status and that it is acting as such, the establishment receiving the service, and the supplier's establishment position. A VAT number alone establishes none of these facts. A supplier's fixed establishment that does not intervene in the supply can be disregarded for liability purposes under Article 192a. The Commission also describes the case of a non-taxable legal entity registered for VAT. See the European Commission's persons liable for VAT guidance.

Domestic ordinary SaaS supplies normally follow domestic supplier-accounting rules. Specific domestic reverse charge regimes exist, so comparing two country codes is not a universal tax rule. Goods, property-related services, events, special schemes, exemptions and other place-of-supply exceptions need their own analysis and are outside this flow.

What VAT validation proves

VIES supplies registration evidence. Article 18 of Implementing Regulation 282/2011 describes evidence for customer status, including VAT-number confirmation and, where a customer has applied for a number but has not received it, other proof with reasonable verification. Contrary information and the capacity in which the customer buys still matter. Missing or invalid numbers are reasons to resolve the evidence, not an automatic finding that a customer is a consumer.

The January 2020 VAT-number condition for the intra-Community goods exemption must not be copied into a universal rule for services. Keep validation evidence with the transaction record, alongside your separate status, establishment and tax-treatment assessment. The EU guidance on VIES checks explains invalid results and recommends retaining a record of validation.

A registration-evidence flow for your backend

1. Collect the customer's VAT number and business details. Route missing evidence for review.
2. Request a fresh VIES check. Distinguish a completed invalid check from an unavailable check.
3. Save the result, original timestamp, source and request ID, including any consultation number returned.
4. Use that evidence in your separate assessment of customer status, establishment and the applicable rules.

The following self-contained TypeScript function runs server-side on Node.js 20 or later. Save it as registration-evidence.ts, set AVATCADO_API_KEY to your live API key, and import checkRegistration in your backend. It uses native fetch because the published Node SDK does not expose the fallback-control parameter. It calculates no VAT and never labels a customer B2C.

type Evidence = {
  vat_number: string | null;
  requested_at: string | null;
  source: string | null;
  source_status: string | null;
  cached: boolean | null;
  stale: boolean | null;
  request_id: string | null;
  consultation_number: string | null;
  proof_status: "provided" | "not_provided";
};
type CheckResult = {
  status: "Verified" | "Invalid" | "Unavailable" | "Error";
  code?: string;
  evidence: Evidence | null;
};

// Server-side Node.js 20+. This records registration evidence, not tax treatment.
export async function checkRegistration(
  vatNumber: string,
  requesterVatNumber?: string,
): Promise<CheckResult> {
  const apiKey = process.env.AVATCADO_API_KEY;
  if (!apiKey) return { status: "Error", code: "missing_api_key", evidence: null };
  const normalize = (value: string) => value.toUpperCase().replace(/[\s.-]/g, "");
  const vat = normalize(vatNumber);
  if (!vat) return { status: "Error", code: "missing_parameter", evidence: null };

  const url = new URL("https://api.avatcado.com/v1/validate");
  url.searchParams.set("vat_number", vat);
  url.searchParams.set("cache", "false");
  url.searchParams.set("fallback", "false");
  // Supply only a genuine requester VAT number. Non-EU sellers can omit it.
  if (requesterVatNumber?.trim()) {
    url.searchParams.set("requester_vat_number", normalize(requesterVatNumber));
  }
  const controller = new AbortController();
  const timer = setTimeout(() => controller.abort(), 15_000);
  let evidence: Evidence | null = null;
  try {
    const response = await fetch(url, {
      headers: { Authorization: "Bearer " + apiKey },
      signal: controller.signal,
    });
    const record = (value: unknown): Record<string, unknown> =>
      value !== null && typeof value === "object" ? value as Record<string, unknown> : {};
    const text = (value: unknown): string | null =>
      typeof value === "string" && value.length > 0 ? value : null;
    let body: Record<string, unknown>;
    try {
      body = record(await response.json());
    } catch (error) {
      if (controller.signal.aborted || !(error instanceof SyntaxError)) throw error;
      return { status: response.status === 503 ? "Unavailable" : "Error",
        code: response.status === 503 ? "http_503" : "malformed_response", evidence };
    }
    const data = record(body.data);
    const meta = record(body.meta);
    const error = record(body.error);
    const consultation = text(data.consultation_number);
    evidence = {
      vat_number: text(data.vat_number), requested_at: text(data.requested_at),
      source: text(meta.source), source_status: text(meta.source_status),
      cached: typeof meta.cached === "boolean" ? meta.cached : null,
      stale: typeof meta.stale === "boolean" ? meta.stale : null,
      request_id: text(meta.request_id), consultation_number: consultation,
      proof_status: consultation ? "provided" : "not_provided",
    };
    if (!response.ok || body.error !== undefined) {
      const code = text(error.code) ?? "http_" + response.status;
      const unavailable = response.status === 503 && (
        code === "upstream_unavailable" || code === "upstream_member_state_unavailable" || code === "http_503"
      );
      return { status: unavailable ? "Unavailable" : "Error", code, evidence };
    }
    if (typeof data.valid !== "boolean" || data.vat_number !== vat ||
        !evidence.requested_at || !Number.isFinite(Date.parse(evidence.requested_at))) {
      return { status: "Error", code: "malformed_response", evidence };
    }
    // Without a requester, cache=false can still return outage cache. Check every response.
    if (meta.source !== "vies" || meta.source_status !== "live" ||
        meta.cached !== false || meta.stale !== false) {
      return { status: "Unavailable", code: "fresh_check_unavailable", evidence };
    }
    return { status: data.valid ? "Verified" : "Invalid", evidence };
  } catch (error) {
    if (controller.signal.aborted) return { status: "Unavailable", code: "timeout", evidence };
    if (error instanceof TypeError) return { status: "Unavailable", code: "network_error", evidence };
    return { status: "Error", code: "unexpected_error", evidence };
  } finally {
    clearTimeout(timer);
  }
}

Call await checkRegistration(customerVatNumber), or pass your genuine requester VAT number as the second argument if you have one. A non-EU seller should omit that argument when it has no suitable VAT registration. Never substitute an invented number or an OSS/IOSS scheme identifier.

• Verified: an explicit live, noncached VIES response reports a valid registration.
• Invalid: an explicit live, noncached VIES response reports an invalid registration.
• Unavailable: a timeout, upstream outage, or response that cannot establish a fresh VIES check. Queue a retry or review.
• Error: input, authentication, quota or response errors. Preserve the code and resolve the operational issue.

These are application outcomes, not additional API statuses. Neither Invalid nor Unavailable determines the VAT rate. Give customers a way to correct their details and resolve the treatment before finalizing an invoice. Without a requester VAT number, an outage can still return stored evidence even with cache=false and fallback=false. Inspect the response metadata. An older consultation number must not be presented as proof of a new check.

Consultation numbers

A genuine requester VAT number allows VIES to return a consultation number where supported. Store it when supplied; it is not guaranteed. Missing proof is explicitly represented as consultation_number: nulland proof_status: "not_provided" in the example. A consultation number supports your record of a check, not a guarantee of the transaction's tax treatment.

Supplying requester_vat_number disables cache reads and national register fallback by default. With those defaults, an upstream outage returns a refunded 503 instead of a stored result. Explicit cache=true restores cache use, including stored outage results; fallback=true permits an eligible national register answer on a supported plan. Neither option guarantees a new consultation number. The example keeps both flags explicitly false and still checks the response metadata.

A request without a requester VAT number:

curl --max-time 15 "https://api.avatcado.com/v1/validate?vat_number=FR82542065479&cache=false&fallback=false" \
  -H "Authorization: Bearer $AVATCADO_API_KEY"

To request a consultation number, append &requester_vat_number=YOUR_GENUINE_VAT_NUMBER. This illustrative success response includes one; the field can be absent:

{
  "data": {
    "valid": true,
    "vat_number": "FR82542065479",
    "country_code": "FR",
    "company": null,
    "consultation_number": "WAPIAAAAA1BBB2",
    "requested_at": "2026-09-15T10:00:00Z"
  },
  "meta": {
    "request_id": "550e8400-e29b-41d4-a716-446655440000",
    "source": "vies",
    "source_status": "live",
    "cached": false,
    "stale": false
  }
}

Invoice and reporting obligations

Once you have established that reverse charge applies, use the applicable invoice rules and the required reverse charge wording. For EU suppliers, the invoice normally includes both parties' VAT numbers; non-EU suppliers should check the applicable national requirements. EU recapitulative-statement obligations for relevant intra-EU services do not automatically apply to a US supplier. See the invoice requirements guide and the US SaaS guide.

Revalidation

Registrations and customer circumstances can change. Choose a documented revalidation policy for recurring billing and review changed details. A monthly or quarterly schedule is an operational choice, not a universal legal interval. Request fresh checks when your policy requires them, and retain the original timestamps of cached evidence. Cached calls still count toward your Avatcado monthly quota.

Get started

Avatcado's free tier includes 500 validations per month. Consultation numbers can be requested on all plans. Read the SaaS billing integration guide or the API documentation for integration details.

Start validating for free →