Special Economic Zone Units ( SEZ Units ) are Exempt from the compliance of e-Invoicing mandate, as per Notification No. 61/2020 - Central Tax, dated 30th July 2020. The same was also clarified via FAQ's on GST e-invoice / IRN System, issued by GSTN Network, dated 11th November 2020 ( 11/11/2020 ). You can refer FAQ Question No. 17 for your reference.
However "SEZ Developers" are required to issue e-invoice, if they have the specified turnover and fulfilling other conditions [ Question No. 19 of FAQ ].