Foreigners visiting Darjeeling must possess and Indian visa. No special permits is required for those coming to Darjeeling by air through Bagdogra airport, and proposing to stay in Darjeeling town for not more than 15 days. However, they need to repot to the Foreigners Registration Office at Bagdogra airport on arrival or at Darjeeling Megistrate Office while during there stay.
Those travelling by rail or road are required to get there pasport and visa get stamped and approval for there stay in Darjeeling at specific Offices. To visit Kalimpong, this permit has to be endorsed at the Foreigners Registration Office in Darjeeling or, alternatively, at the office which issued it.
For Indian nationals no such Permits are required at all, however it is advisable to carry any of the Indian Identification Documents for Safety and incase if opt for Sikkim Trekking trip later during the trip.