The contribution deals with the Revenue Registry Act case partially abolished by the Czech Constitutional Court. It introduces, describes and critically analyses the revenue registry in the Czech Republic with regard to those provisions attached by the decision of the Court and confirms the hypothesis that the decision of the Court is illegal: the Court does not have the power to cancel the start of the third and fourth phases of the electronic revenue registry, since there was no such petitioners’ proposal. Doing so, the Constitutional Court breached the principles of equality, non-discrimination, and predictability.