This ban on the handsets with out the IMEI number comes as a security measure amid the increased terror threat across the country.
The 15-digit number is crucial for security agencies to trace calls made from and received on handsets.
The number which is automatically registered with the mobile service provider as soon as the phone is activated represents the manufacturer's name, and type of the phone.
With over 25 million handsets without IMEI numbers in circulation, GSM mobile operators lobby Cellular Operators Association of India installed identity number on devices without this number, as per the government directive.
And since a large fraction of the users are yet to avail the number, the mobile operators have sought a two-month extension of the deadline.