Mega-projects due to their cross-border nature are increasingly influenced by the evolving international tax framework. The successful execution of these projects and, indirectly, the significant positive spillovers effects which can be triggered, hinges on navigating complex legal environments that can either foster or hinder their development. Tax and in general regulatory considerations are crucial as they shape the ecosystem in which such large-scale initiatives can thrive, directly affecting their positive economic outcomes. Given the inherently international nature of mega-projects, the notion of permanent establishment come into play as cornerstone concept in international taxation. This analysis will explore certain nuances of the PE concept within the context of mega-projects, adopting and evolutive view of the relevant provision and stressing the latest amendments that occurred both at international and at Italian level. Understanding the intricacies of PE is therefore essential for stakeholders to navigate international tax issues effectively, ensuring that mega-projects are structured in a way that minimizes legal and financial risks while maximizing their potential for success.