Tax Authorities Can Use Illegally Obtained Evidence, Confirms the Court

On June 19, 2025, the Court of Cassation, in plenary session, ruled: the tax administration can use evidence obtained in an irregular manner, as long as it meets certain conditions. This decision affirms the so-called “Antigone case law,” which has already been applied in tax matters since 2015, but until now only confirmed in the Dutch-speaking section.

Legal Basis

Inspired by a 2003 criminal ruling, the Antigone case law allows the use of illicit evidence under three conditions:

1. Compliance with required formalities under penalty of nullity: If the law requires an act (e.g., a search authorized by a judge), its absence makes the evidence inadmissible.
2. Reliability of the evidence: The evidence must not be tainted by major doubt.
3. Respect for the right to a fair trial (Article 6 ECHR).The Court judges that this practice does not infringe the Constitution, as evidence is not considered an “essential element of tax.”

Critical Reactions

Legal experts question the principle of legal certainty itself. They point out that this case law:

• Ignores existing legal provisions regarding admissible evidence;
• Opens the door to problematic retroactivity in tax matters;
• Does not effectively prevent arbitrariness, given the lack of clear criteria. Some taxpayers affected by this decision may take their case to the European Court of Human Rights (ECHR) for violation of the principle of non-retroactivity.

Current Status and Future Prospects

The government is considering legally regulating the use of such evidence. The coalition agreement thus provides for the creation of a clear framework to limit abuses.