The empirical nearest‐neighbor tight binding theory and the Harrison bond‐orbital model are exploited to investigate the variation in effective band gap, electron effective masses and dielectric constants induced by non‐stoichiometry. A model is proposed to describe absorption edges in heavily‐doped InN using the Efros‐Shklovslii approach for compensated semiconductors and taking into account the non‐parabolicity of the InN band structure. Reasonable agreement with experimental trends has been demonstrated. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)