The asymmetric unit of the title compound, C(10)H(13)NO(4)S, comprises two crystallographically independent mol-ecules. The crystal structure is stabilized by weak inter-molecular C-H⋯O hydrogen bonds, which link mol-ecules along the b axis. The crystal is a nonmerohedral twin, the refined ratio of the twin components being 0.344 (2):0.656 (2).