Inclines are the additively idempotent semirings in which the products are less than or equalto factors. Thus inclines generalize Boolean algebra, fuzzy algebra and distributive lattice.And the Boolean matrices, the fuzzy matrices and the lattice matrices are the prototypicalexamples of the incline matrices (i.e., the matrices over inclines). In this paper, the completedescription of the invertible incline matrices is given. Some necessary and sufficientconditionsfor an incline matrix to be invertible are studied, Cramer’s rule over inclines is presented andthe group of invertible incline matrices is investigated. The main results in the present papergeneralize and develop the corresponding results in the literatures for the Boolean matrices,the fuzzy matrices and the lattice matrices.