2-Amino-4,6-dimethyl-pyrimidin-1-ium 1-oxo-2,6,7-trioxa-1λ-phosphabicyclo-[2.2.2]octane-4-carboxyl-ate.

In the title compound, C(6)H(10)N(3) (+)·C(5)H(6)O(6)P(-), the cation and anion are linked by pairs of N-H⋯O hydrogen bonds. There are additional inter-molecular N-H⋯N hydrogen bonds, which generate centrosymmetric tetramers of two cations and two anions.