Add to ORKGR factor = 0.056; wR factor = 0.148; data-to-parameter ratio = 13.1. The title molecule, C5H5N5O3S, is approximately planar, with a maximum deviation from the mean plane through the non-H atoms of 0.182 (3) A ̊ for the amine N atom. In the crystal, molecules are connected via N—H O and N—H S interactions, building a three-dimensional hydrogen-bonded network. Additionally, a weak intramolecular N—H O hydrogen bond is observed. Related literature For the synthesis of alloxan-5-thiosemicarbazone, see: Beyer et al. (1956). For the antibacterial activity of alloxan-5-thio-semicarbazone against Staphylococcus aureus and Escherichia coli, see: Douros et al. (1973)