The title compound, C(12)H(13)NO(3)S, was synthesised by the reaction of benzo[d]isothia-zol-3(2H)-one with butyl alcohol in toluene. The benzoisothia-zolone ring system is almost planar with a mean deviation of 0.041 (1) Å. In the crystal, mol-ecules are linked by weak inter-molecular C-H⋯O hydrogen bonds.