In the title mol-ecule, C(22)H(15)Cl(2)NO(4)S, the heterocyclic thia-zine ring adopts a half-chair conformation, with the S and N atoms displaced by 0.343 (5) and 0.402 (5) Å, respectively, on opposite sides of the mean plane formed by the remaining ring atoms. The mol-ecular structure is consolidated by an intra-molecular O-H⋯O hydrogen bond, which generates an S(?) ring. In the crystal, the molecules are linked by C-H⋯O interactions into [010] chains.