In the title mol-ecular salt, C(5)H(9)N(2) (+)·C(7)H(3)N(2)O(7) (-), the roughly planar anion (r.m.s. deviation = 0.120 Å) has been deprotonated at the phenol group. An intra-molecular O-H⋯O hydrogen bond in the anion generates an S(6) ring. In the crystal, the components are linked by cation-to-anion N-H⋯O and N-H⋯(O,O) hydrogen bonds, generating [010] double chains. Weak C-H⋯O inter-actions consolidate the packing.