Ammonium hydrogen squarate–water (3/2)

In the title compound, NH₄⁺·C₄HO₄^?·H₂O, the hydrogen squarate anions and water molecules are arranged to form planes almost parallel to bc. The ammonium cations are located between these planes and cross‐link them in the a direction by means of an extensive network of hydrogen bonds. There are two symmetry‐independent sets of cations and anions. One of the hydrogen squarate anions and one of the ammonium cations are situated on a twofold axis and the H atoms of these moieties are disordered over the symmetry‐related sites.