The title compound, C(11)H(11)NO(3)S, was synthesized by the reaction of benzo[d]isothia-zol-3(2H)-one with isopropanol in toluene. The benzoisothia-zolone ring system is essentially planar, with a mean deviation of 0.018 (2) Å from the least-squares plane defined by the nine constituent atoms. In the crystal, mol-ecules are linked by weak inter-molecular C-H⋯O hydrogen bonds.