The title compound, C(14)H(11)N(3)O(5), crystallized with two independent mol-ecules per asymmetric unit. Each mol-ecule assumes an E configuration with respect to the methyl-idene unit. Intra-molecular O-H⋯O and N-H⋯O hydrogen bonds are present in each mol-ecule and they are linked by an O-H⋯O hydrogen bond. The dihedral angles between the mean planes of the two benzene rings are 4.45 (16) and 1.7 (2)° in the two mol-ecules. The crystal structure is stabilized by inter-molecular O-H⋯O and N-H⋯O hydrogen bonds.