Bis[(diamino-methyl-idene)aza-nium] 5-(1-oxido-1H-1,2,3,4-tetra-zol-5-yl)-1H-1,2,3,4-tetra-zol-1-olate.

The anion of the title salt, 2[C(NH(2))(3)](+)·C(2)N(8)O(2) (2-), lies on a center of inversion and its two five-membered rings are coplanar. The guanidinium cation forms N-H⋯O and N-H⋯N hydrogen bonds to the anion, generating an eight-membered ring. Other hydrogen bonds lead to the formation of a three-dimensional network.