In the title mol-ecule [systematic name: 1,1,1',1'-tetra-oxo-2,2'-(oxydimethyl-ene)bi(1,2-benzothia-zol-3-one)], C(16)H(12)N(2)O(7)S(2), the benzisothia-zole ring systems are individually planar [maximum deviations of 0.0497 (13) and 0.0195 (19) Å] and their mean planes are inclined at a dihedral angle of 62.76 (4)°. The crystal structure is stabilized by weak inter-molecular C-H⋯O inter-actions. Two O atoms bonded to two S atoms and four aryl H atoms belonging to two symmetry-related mol-ecules lying about an inversion center form a hydrogen-bonded 10-membered ring with graph-set notation R(4) (2)(10).