“Old” constitutional principles on tax law clarity in the post-BEPS era – tax system efficiency above all else?

This problem is particularly topical in the context of the current global initiatives to combat tax avoidance, and therefore primarily the BEPS project. At the time of its launch, the need for cooperation between all countries (not
only OECD members) was quite strongly emphasized. In some cases, such cooperation is a guarantee of the success of the project (it is already known that it will not be possible owing to the attitude of the USA). However, this raises the question of whether the global initiative will mean depriving countries of their tax sovereignty. If the project is to be implemented in all countries, parliaments will lose real influence on the shape of the tax system. How to reconcile the effective fight against fraud with democratic principles? Additionally, the Polish reality shows a tendency to use the BEPS project (and sometimes the related EU regulations) to justify very often much more restrictive solutions introduced into Polish tax law for taxpayers.