In Germany, it is undisputed that the fundamental rights of the German constitution, the Basic Law (Grundgesetz), set limits for tax legislation at the national level. It has not yet been fully clarified whether and to what extent legal acts of the European legislator in the field of taxation must be measured against the standard of the Charter of Fundamental Rights of the EU (CFR). In a ground-breaking ruling of 8 December 2022 (C-694/20), the CJEU has now affirmed this in relation to Directive (EU) 2018/822, which provides for an EU-wide reporting obligation with regard to cross-border tax arrangements. The CJEU declared a specific provision of the said directive invalid due to a violation of the fundamental right under Article 7 CFR to respect for private communications. This paper sets out the far-reaching consequences of the CJEU’s ruling for the directive in question in particular, and for EU tax directives in general.