O ZFM model can be seen as an example of successful public policy because it has contributed over the last 50 years to the development of the region. This article deals with the legal nature of the tax incentives offered by the ZFM. The discussion on this topic is striking and very important for the future of the State and the Region, as well as for Brazil, which is experiencing a delicate adjustment situation, mainly in the public accounts and the tax system, which have struggled to collapse. The objectives of this study are: present the ZFM model, focusing on its peculiarities; analyse the concepts of tax exemption and immunity, establishing the main differences between these institutes; present the various rulings of the STF dealing with the legal nature of the tax incentives in the ZFM; and present all incentives at federal, state and municipal levels, establishing their legal nature. The methodology used used the literature search, using the hypothetical deductive method to analyse the concepts of tax exemption and immunity in order to arrive at the definition of the fiscal nature of the incentives of the ZFM model. Although this work does not seek to exhaust the issue, it aims to raise interest in preserving and upsetting this model, which, despite some critics, has greatly contributed to reducing regional inequalities and preserving the amazonic environment.