The development of NH transfer reactions using hypervalent iodine and simple sources of ammonia has facilitated the synthesis of sulfoximines and sulfonimidamides for applications across the chemical sciences. Perhaps most notably, the methods have been widely applied in medicinal chemistry and in the preparation of biologically active compounds, including in the large-scale preparation of an API intermediate. This review provides an overview of the development of these synthetic methods involving an intermediate iodonitrene, since our initial report in 2016 on the conversion of sulfoxides to sulfoximines. This review covers the NH transfer to sulfoxides and sulfinamides, and the simultaneous NH/O transfer to sulfides and sulfenamides to form sul-foximines and sulfonimidamides respectively. The mechanism of the reactions and identification of key intermediates are discussed. Developments in the choice of reagents and in the reaction conditions and set-ups used are described.