VAT Number Validation: The Complete Guide for 2026

VAT number validation sounds simple. You have a number. You check whether it is real. But in practice, finance teams and developers run into the same problems repeatedly: VIES returns blank names for German companies, numbers that look correct get rejected by clearance systems, and the difference between a VAT registry and a business registry is genuinely confusing.

This guide covers everything you need to know about VAT number validation in 2026 — what a VAT number is, why validation matters, how EU VIES works, format rules for major countries, common errors, and when to use an API.

What is a VAT number?

A VAT number (also called a VAT registration number or VAT ID) is a unique identifier assigned to a business by its national tax authority when that business registers for Value Added Tax. In the EU, VAT numbers are governed by EU Directive 2006/112/EC and always start with a two-letter ISO country code prefix.

Outside the EU, the terminology varies. The UK calls them VAT registration numbers. Norway uses organisasjonsnummer with an MVA (merverdiavgift) suffix. Brazil has CNPJ (Cadastro Nacional da Pessoa Jurídica) for companies. The concept is the same — a tax authority assigned identifier that proves a business is registered to charge and reclaim VAT or equivalent consumption taxes.

It is important to distinguish a VAT number from a general business identifier. A company number (like a UK Companies House number, a German Handelsregisternummer, or a French SIRET) records legal incorporation. A VAT number records VAT registration. A business can be legally incorporated without being VAT-registered if its turnover is below the registration threshold. Conversely, a VAT number can remain valid even after a company goes dormant.

Why validation matters

Three reasons drive the business case for VAT number validation.

Invoice rejection prevention. Countries with e-invoicing mandates validate VAT numbers at submission. Italy's SDI validates the partita IVA of both supplier and buyer before accepting a FatturaPA document. Poland's KSeF checks the NIP of both parties on submission. Belgium's Peppol infrastructure will not route an invoice to a Peppol participant that does not exist. An invoice submitted with an invalid VAT number is rejected — and a rejected invoice is a delayed payment, with correction and resubmission work to follow.

VAT reclaim validity. For VAT-registered buyers, the right to deduct input VAT depends on receiving a valid VAT invoice from a VAT-registered supplier. If your supplier's VAT number is invalid, your VAT reclaim is at risk. This is particularly relevant for finance teams processing high volumes of supplier invoices across multiple countries.

Compliance and fraud prevention. Invalid or fictitious VAT numbers are a known vector for VAT carousel fraud. For businesses selling to other businesses, validating the buyer's VAT number is a basic due diligence step — especially for zero-rated B2B transactions where the VAT treatment depends on the buyer being VAT-registered.

EU VIES explained

VIES (VAT Information Exchange System) is the European Commission's central VAT validation system. It connects the VAT registries of all 27 EU member states and lets you verify, in real-time, whether a VAT number is currently registered and active.

VIES does not hold its own database. When you query VIES for a German VAT number, VIES forwards your query to the German Bundeszentralamt für Steuern and returns their response. This means VIES reflects the current state of each member state's registry.

What VIES checks. VIES validates that a VAT number is currently registered and active in the member state it claims. It returns a yes/no answer plus, in most cases, the registered company name and address.

Qualified consultations. VIES offers a standard consultation and a qualified consultation. A qualified consultation requires you to provide your own VAT number — if both numbers are valid, VIES issues a consultation number that you can keep as documentary evidence of due diligence. This is useful for zero-rated B2B transactions where you are applying the reverse charge.

When VIES returns blank names. Some member states do not share company names or addresses via VIES for data privacy reasons. Germany is the most common case — VIES will confirm a German VAT number is valid but will return an empty name field. This does not mean the number is invalid; it means the German authority does not expose name data through VIES. You need to check the German Unternehmensregister separately for company name confirmation.

Format guide for major countries

Each country's VAT number follows specific format rules. Here is a reference table for the largest economies:

Several countries use weighted checksum algorithms to validate numbers at format level. The German algorithm applies modulus 11 across the 9 digits. The Polish NIP uses a fixed weight array and modulus 11. Format-level validation catches the most common typographic errors without needing to hit any external registry.

Common errors and how to fix them

O instead of 0 (letter O vs digit zero). This is the most frequent data entry error, particularly in countries where the VAT number contains both letters and digits in the prefix or suffix positions. Automated alternative-matching in your validation layer should try substituting common O/0 and I/1 swaps before returning an error.

Missing country prefix. Users sometimes enter only the local number without the country prefix — 811428983 instead of DE811428983. If you know the country context (for example, the billing country in your CRM), you can prepend the expected prefix and retry.

Spaces and punctuation. Some authorities display VAT numbers with spaces or dots (e.g. DE 811 428 983 or IT 02.118.311.006). Strip all non-alphanumeric characters before validation.

Outdated numbers in CRM. A VAT number valid at onboarding may become invalid if a business deregisters, goes dormant, or restructures. Periodic re-validation of existing customer and supplier records catches these before they cause invoice rejections.

Cross-border confusion. Companies operating across borders may have multiple VAT registrations. A German subsidiary of a French group has a German VAT number (DE...) and the French parent has a French VAT number (FR...). Validating the wrong number against the wrong country will always fail. Ensure your data model stores the country-specific VAT number alongside the country code.

National registries vs VAT registries

The distinction matters for different use cases. A VAT registry validates VAT registration status. A national business registry validates legal existence.

For invoicing compliance, VAT registry validation is what you need. An invoice with an invalid VAT number will be rejected by e-invoicing mandates regardless of whether the business exists as a legal entity.

For customer onboarding and KYB, national business registries are useful because they cover businesses below the VAT threshold too. The UK Companies House, Norwegian Brreg, French INSEE (SIREN/SIRET), and Brazilian CNPJ system are all business registries that record incorporated entities regardless of VAT status.

Several countries have registration numbers that serve both functions. Denmark's CVR number is used as both the business identifier and the VAT identifier (with the DK prefix added for VIES). Norway's organisasjonsnummer from Brreg, with the MVA suffix, serves as the VAT identifier. Clearvo's API covers both types and returns the registry field so you know exactly which was queried.

API approach vs manual

Manual VAT validation — logging into VIES, entering numbers one at a time — is impractical at any scale. It is not auditable, it is not embeddable in workflows, and it does not handle the alternative-matching logic needed to catch common entry errors.

An API approach gives you validation at the point of data entry (onboarding forms, supplier import workflows), automated re-validation of existing records, documentary evidence of each check with timestamps, and normalised output regardless of input format.

Clearvo's TIN Validation API, announced in June 2026, covers 100+ countries with real-time registry lookups.

Clearvo's TIN Validation API covers 100+ countries including all 27 EU VIES member states, UK HMRC, Norwegian Brreg, French SIREN, Danish CVR, Brazilian CNPJ, and more. EU VIES lookups are free on all plans. Documentation is at /docs.

Questions? Email hello@clearvo.io — we respond within one business day.