In the title 2:1 co-crystal, 2C4H5ClN4·C4H6O4 the complete succinic acid mol-ecule is generated by a crystallographic centre of symmetry. In the crystal, pairwise O-H⋯N and N-H⋯O hydrogen bonds link the pyrimidine and succinic acid mol-ecules, generating R 2 2(8) loops. The pyrimidine mol-ecules are linked by pairwise N-H⋯N hydrogen bonds, again generating R 2 2(8) loops. Collectively, the hydrogen bonds link the components into corrugated (100) sheets. The Hirshfeld surface is presented.