In the title compound, C(8)H(9)ClN(2)O(3)S, the benzene ring makes a dihedral angle of 4.1 (9)° with the amido -NHCO- plane including the major occupancy component of the carbonyl O atom [19 (4)° for the minor component]. An intra-molecular C-H⋯O inter-action occurs. The O atom of the carbonyl group is disordered over two positions with site-occupancy factors of 0.67 (11) and 0.33 (11). Inter-molecular N-H⋯O hydrogen bonds help to stabilize the crystal structure.