2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/102240The characteristic function has been an important tool for studying completely non unitary contractions on Hilbert spaces. In this note, we consider completely non-coisometric contractive tuples of commuting operators on a Hilbert space $\clh$. We show that the characteristic function, which is now an operator valued analytic function on the open Euclidean unit ball in $\mathbb{C}^n$, is a complete unitary invariant for such a tuple. We prove that the characteristic function satisfies a natural transformation law under biholomorphic mappings of the unit ball. We also characterize all operator-valued analytic functions which arise as characteristic functions of pure commuting contractive tuples.18 pages, revised version, to appear in Proc. Math. Sci., Indian Acad. SciOperator Algebras47A13; 47A20; 47A56text