The financial crisis of 2008 highlighted the need to find new sources of economic growth. Innovation is one of such underutilized ressources in Europe. It is generally admitted that tax incentives stimulate investment in research and development (R&D). The current research project aims at elaborating a harmonized R&D tax concept and providing an explanatory research book to aid decision makers at national and European level. The goal of this article is to present and discuss the postulate, theoretical framework, methodology, and main findings of the project which is now coming to an end. The issue of research and development (R&D) tax incentive is very topical. It is also at the centre of a policy position with opposes direct subsidies to tax incentives. One reason for opposition might be the general aim of countries to attract companies to foster job creation through highly qualified work. Of equal importance is the generation of intellectual property (IP) as a possible outcome of R&D activities. IP is critical for the global allocation of tax revenues. Although apparently technical, a harmonized tax concept touches upon many fundamental issues of tax law such as discrimination, 'tax neutrality', and interpretation of tax statutes and regulations. The scope of concepts (contained in a definition section) is an essential item as well. R&D is indeed a good example of how difficult tax interpretation can be, even if a common threshold for collecting statistics about R&D is already supplied by the Frascati Manual. The Frascati Manual provides a good starting point for a common approach. However, the Frascati Manual suffers two main defects. First, it is drawn up by a team of experts and, as such, lacks democratic legitimacy. In addition, it is not compulsorily applied by all national legislators. Second, some recommendations of the Frascati Manual concerning, for example, the domain of research (e.g. humanities) are excluded by certain national legislation (e.g. as in the case of Ireland). This is one of the main reasons why the results of this research (Statements No. 1 and 2) aim to remove the divergent applications despite a common starting point. The second result of the research concerns eligible expenses, identified for a long time in the national legislation as being very diverse. Consequent, Statements No. 3-9 therefore propose a common approach. These statements should therefore help to reduce negative effects resulting from legal fragmentation. They could contribute to shaping of a new tax legal order, particularly within the European Union.