The asymmetric unit of the title compound, C(20)H(18)ClN(5)O(3)S, contains two independent mol-ecules with significantly different conformations of the heterocyclic thia-zine rings. In both mol-ecules, the thia-zine rings adopt half-chair conformations, with the S atoms displaced by 0.382 (3) and 0.533 (3) Å and N atoms -0.351 and -0.275 Å, respectively, from the planes formed by the remaining ring atoms. The crystal structure is stabilized by weak inter-molecular N-H⋯O and C-H⋯O inter-actions.