In March 2019, the Constitutional Court had to consider whether the obligation for lawyers to file an annual listing of clients who are taxable for VAT purposes with the tax authorities is compatible with the duty of professional secrecy. Such listing discloses the identity of clients with whom the lawyer has carried out transactions for a total amount exceeding EUR 250 (approximately USD 293) to the authorities. The Constitutional Court held that the duty of professional secrecy does not prevent such filing because the information filed does not concern lawyers' core activities; it is not related to confidential information disclosed by a client that is potentially incriminating.
On 24 September 2020, the Constitutional Court partially annulled the Anti-Money Laundering Act of 18 September 2017 (AMLA) based on legal privilege. Under the AMLA, lawyers were obliged to report any suspicion of money laundering or terrorist activities by clients to the Financial Intelligence Processing Unit (Cel voor Financiële Informatieverwerking (CFI)/ Cellule de Traitement des Informations Financières (CTIF)) , even when the client had withdrawn the suspicious transaction, following the lawyer's advice. The Constitutional Court held that, in such case, the reporting obligation conflicts with lawyers' duty of professional secrecy because the information received is covered by legal privilege and therefore annulled this aspect of the reporting obligation. This annulment was extended to reporting obligations of lawyers' employees because no person external to the relationship between the lawyer and their client should ever be obliged to report legally privileged information to the CFI.
This decision reaffirmed the fundamental importance of legal professional privilege in the lawyer-client relationship. Nevertheless, the Anti-Money Laundering Act of 18 September 2017 continues to impose certain obligations on lawyers, particularly regarding the maintenance of the ultimate beneficial owners (UBO) register. When a lawyer identifies a discrepancy between the information available on a company's beneficial owners and the data recorded in the UBO register, they are not permitted to report it directly to the treasury administration. Instead, they must notify the chair of their bar, who is responsible for assessing whether the legal conditions for lifting professional secrecy are met. Only if these conditions are satisfied may the Chairman of the bar transmit the relevant information to the authorities.
The Constitutional Court, in its judgment of 16 February 2023 ruled that, this specific procedure - challenged by accountants and tax advisors - the difference in treatment between the lawyers and the accountants and tax advisors is justified by the need to safeguard the rights of the defense and the right to privacy, which are particularly sensitive in the context of legal representation. As such, the Chairman of the bar's intervention is deemed necessary to preserve these fundamental protections in the legal profession.
In its judgment of 19 October 2021, the Supreme Court clarified the scope of application of the duty of professional secrecy with respect to information not received directly by lawyers from a client. The Supreme Court held that an (oral) conversation between a defendant's lawyer in criminal proceedings and another codefendant, which reveals incriminating information regarding the lawyer's client, is covered by that lawyer's duty of professional secrecy. Therefore, the content of such a conversation may not be intercepted during investigations or used in legal proceedings.
Finally, the Court of Appeal in Ghent confirmed on 3 February 2020 that the duty of professional secrecy applies regardless of the medium on which the information was communicated. If a communication technique is used that allows information to be consulted by third parties, legal privilege will only lapse if the information is also addressed to third parties. In particular, any communication sent to a client's professional email address, which may, from a technical point of view, be accessed by their employer, still falls under the duty of professional secrecy. This is also the case if the accessing party is a counterparty in legal proceedings.