Arno began his career as a lawyer at the Brussels Bar in 2020. He joined a Brussels law firm in the same year, where he focused on tax law with a specialization in international tax law, covering personal and corporate income tax.

In 2023, Arno decided to continue his career at another leading law firm in Brussels, where he further deepened his knowledge of tax law. He mainly focused on files related to tax estate planning, compliance analysis, tax regularizations, applying for an advance ruling (ruling procedure) and life insurance taxation.

As of 2025, he strengthens Andersen's tax team.