The asymmetric unit of title compound, C(7)H(6)N(2)O(4), contains two mol-ecules, one of which has a disordered nitro group with an occupancy ratio of 0.517 (9):0.483 (9) for the O atoms. Both mol-ecules contain an intra-molecular O-H⋯O hydrogen bond. In the crystal, both mol-ecules form inversion dimers linked by pairs of N-H⋯O hydrogen bonds, resulting in R(2) (2)(8) ring motifs. The dimers are connected by further N-H⋯O links and weak C-H⋯O inter-actions, resulting in a layered motif.