The potassium p-nitrobenzoxasulfamate monohydrate salt (C6H3N2O5 SK·H2O), was prepared by the reaction of p-nitrobenzoxasulfamate with t-BuOK in the water-THF solution and characterized by C, H, N, S analyses, IR, UV-VIS and 1H NMR spectroscopy. The structure of the compound has been determined by single-crystal X-ray diffraction. The compound crystallizes in orthorhombic system, space group P212121, with Z = 8. The structure consists of chains formed by K polyhedra connected by sulfonyl, nitro and amine groups of the p-nitrobenzoxasulfamate anion and lattice water molecules. Thermal decomposition behavior of the compound was studied by DTA and TG techniques. © 2002 Elsevier Science B.V. All rights reserved.