In the crystal structure of the title proton-transfer compound, CH(6)N(3)O(+)·C(7)H(4)NO(4) (-), O-H⋯O and N-H⋯O hydrogen bonds are formed respectively between the cations and the anions, each component affording a supra-molecular chain along the c axis. The cation and anion chains are further linked by N-H⋯O and N-H⋯N hydrogen bonds. A π-π inter-action is also observed between the pyridine rings; the inter-planar separation and the centroid-centroid distance are 3.3425 (6) and 4.6256 (11) Å, respectively.