The title mol-ecule, C(5)H(5)N(5)O(3)S, is approximately planar, with a maximum deviation from the mean plane through the non-H atoms of 0.182 (3) Å for the amine N atom. In the crystal, mol-ecules are connected via N-H⋯O and N-H⋯S inter-actions, building a three-dimensional hydrogen-bonded network. Additionally, a weak intra-molecular N-H⋯O hydrogen bond is observed.