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Abstract: Heterocycles consistently attract scientific interest due to their unique structures, which have led to several applications in organic chemistry, pharmacology, and materials research. In organic chemistry, a range of reactions that add one or more rings to a molecule are collectively referred to as ring-forming or ring-closing reactions. Heterocyclic ring formation (HCRF) is the process of forming cyclic structures in which other elements, such as nitrogen, oxygen, sulfur, and so on, take the place of carbon atoms. The inexpensive, commercially accessible, inorganic white ionic solid with the formula NH4I is ammonium iodide. It serves as a redox mediator, an electrolyte, a promoter, and the best option for “N” or “iodide” sources (metamorphosis from inorganic to organic) in a variety of synthetic organic transformations. Its applications range from laboratory research to industrial processes. As of date, there are no exclusive reports on the applications of NH4I in catalysis or organic synthesis. In this review (2020 onwards till date), we thoroughly and critically report the applications of this versatile reagent in heterocyclic ring formation reactions that lead to the synthesis of various heterocyclic scaffolds related to simple systems, namely thipophenes, pyridines, thiazoles, isothiazoles, pyrroles, 1,3,5-triazines, pyrazoles, 1,2,4-thiadiazoles and fused systems, namely benzimidazoles, benzothiazoles, quinolines, quinazolines, phenothazines, indolizines, benzoxazoles, fused imidazoles, β-carbolines, etc. In addition to the advantages, the limits of the approaches were also examined. We strongly hope that this compilation will be helpful to researchers and academicians worldwide in exploring further the applications of NH4I in various synthetic organic transformations.