On September 22, 2026, the European Commission published an external study on Taxpayer Identification Numbers (TINs) and TIN verification tools. The study supports the Commission’s work on taxpayer identification under the Directive on Administrative Cooperation (DAC).

What the Study Found

The study found that national TIN systems across the EU vary widely. EU countries use different formats, lengths, structures, issuing authorities, and rules regarding how TINs are used. For individuals, most EU countries issue a TIN automatically, while some assign one only when a person becomes subject to a tax obligation. Some TINs contain personal information, such as a date of birth, whereas others contain no such information.

For businesses, TINs are generally issued when a company or other entity is registered. However, the relationship between TINs and other identifiers, such as VAT numbers or business registration numbers, differs significantly between EU countries. These differences reflect national administrative choices but can create difficulties when information is exchanged across borders.

The study found that the inclusion of TINs in automatic information exchanges under the EU DAC is also inconsistent. Some regimes, including DAC2, DAC7, and DAC8, require the receiving EU country to include the TIN in the information exchanged. Under other DAC provisions, TINs are included only where available or on a voluntary basis. 

As a result, TINs are available for only a limited proportion of some exchanges. Even when a TIN is provided, existing systems generally offer only limited possibilities for checking whether it is valid and correctly linked to the taxable person. Because of these limitations, tax authorities often have to use other identifying information to match incoming data with their national records. They may compare combinations of names, dates of birth, and addresses and, in more complicated cases, carry out manual checks.

The study concludes that introducing a single composite EU TIN, consisting of a country code combined with a national TIN for cross-border reporting, would be technically feasible but is not advisable at this stage. According to the study, implementing such a system would create high costs and disruption for tax authorities and reporting entities, while providing limited additional value because the country that issued the TIN is generally already reported alongside the number.

Instead, the study identifies a stronger need for an EU-wide TIN verification tool. Existing services such as TIN-on-the-Web and VIES-on-the-Web cannot reliably establish across borders whether a TIN is valid and actually belongs to the relevant taxable person.

Conclusion

While creating a unified EU TIN system is currently impractical due to cost and operational friction, establishing a centralized TIN verification tool offers a pragmatic path forward. Enhancing cross-border verification capabilities will significantly improve administrative coordination, reduce reporting errors, and strengthen tax compliance across the EU.