The eIDAS Regulation has become a key and, in a way, a ground-breaking piece of legislation of the European Union. It is crucial, in particular, with regard to its ambitious objectives and ground breaking because it was adopted at a time when the Member States of the European Union already had this issue more broadly or narrowly regulated by national laws. In our scientific study, we focus primarily on the critical analysis of the adopted eIDAS Regulation, its impact on the existing e-signature legislation and the amendments adopted, which are necessary to unify the legal framework for electronic signature of the Member States of the European Union. Our main objective was therefore to analyse the legal aspects of the electronic signature. We draw attention to those areas which, because of the regulation adopted, had to be recast and incorporated into the new Trust Services Act, as it emerged from the eIDAS Regulation for us. When processing the topic, we used legal analysis, compliant and available scientific methods as well as selected application problems from practice. In researching and developing a new legal framework for the electronic signature, we also used scientific and doctrinal interpretations associated with the application of scientific and scientific literature contained in the Web of Science and Scopus databases. The results of the study indicate that, despite the multi-annual effectiveness of the eIDAS Regulation, there are still problems that need to be addressed by amending it.