On conditions determining formal automorphisms of integro-differential operators

Results providing conditions on a family of integro-differential operators to determine a formal automorphism are established. Equivalently, the problem can be read in terms of existence and uniqueness of formal solutions of Cauchy problems in different settings. The main achievements provide a three-statement result not only in the framework of general formal power series, but also on subspaces appearing in applications such as Gevrey settings and moment differential operators.