The title compound, C12H20N2O4, represents one example of a zwitterionic imidazolium salt with a carboxyl-ate group at the 2-position of the imidazolium ring. The dihedral angle between the heterocyclic ring and the carboxyl-ate group is 31.3 (1)°. The side chain linking the N atom of the ring and the methine C atom has a gauche-anti-anti conformation [torsion angles = -60.3 (2), -175.7 (2) and 178.7 (2)°, respectively]. In the crystal, mol-ecules are linked by short C-H⋯O hydrogen bonds involving the C-H groups in the aromatic ring to generate (001) sheets.