In the title compound, C(15)H(12)N(2)O(5)S, the benzisothia-zole group is approximately planar (r.m.s. deviation excluding H atoms and the two O atoms bonded to S = 0.023 Å). The dihedral angle between the benzisothia-zole ring and the terminal phenol ring is 84.9 (1)°. In the crystal, mol-ecules are joined by N-H⋯O and O-H⋯O hydrogen bonds, and π-stacking inter-actions are observed between alternating phenol and benzisothia-zole rings [centroid-centroid distances = 3.929 (3) and 3.943 (3) Å].