Entry permits to Sikkim
As of May 2015, it is still necessary to obtain a Restricted Area Permit (also known as Inner Line Permit - ILP) for foreigners to travel in Sikkim. The permit is a piece of paper containing your passport data and dates you are permitted to travel (typically, 15 days). When entering and exiting Sikkim, your passport will be stamped much in the same manner as when crossing national borders. Obtaining a permit is a pure bureaucratic formality and usually takes a few minutes. You will need to fill in an application form and provide a few passport photos (3 to visit tsomgo Lake in East and 3 to visit North Sikkim.
The permit can be obtained when crossing the Sikkim state border by road in Rangpo or Meili. Sikkim Inner like permit for travel form is available online for Sikkim travel and tour https://sikkimtraveltour.com and from Sikkim Tourism Center in Siliguri located at the S.N.T. bus stand (the place from which government buses depart for Sikkim: S.N.T. means "Sikkim Nationalized Transport") in the vicinity of Siliguri Junction railway station (different from New Jalpaiguri station, and reachable from there by taxi/public shared taxi). The website of Ministry of Home Affairs states that permits can also be obtained at large international airports (Delhi, Mumbai, Chennai, Kolkata), but locating the relevant facilities has proven difficult for some travellers, due to incompetence of personnel. Permits can also be applied for at the time of Indian visa application, or at 14 Panchsheel Marg, New Delhi 110021 (011 26115346) and 4/1 Middleton Street, Kolkata 700071 (033 22817905). Within India Inner Line Permits may be issued by:
Sikkim House, 12-14 Panchsheet Marg, Chanakyapuri, New Delhi (Tel.011-2611 5346),
Sikkim Tourist Centre, SNTC Bus Stand, Hill Cart Road, Silguri (Tel.0354-251 2646),
Sikkim Tourist Information Centre, Sikkim House, 4/1 Middleton St., Kolkata (Tel. 033-2281 7905)
Foreign Regional Registration Office in Delhi, Mumbai, Kolkata, Chennai, Darjeeling.
The permit is valid for 2 weeks from the border entry to Sikkim. It can by extended for 2 additional weeks at the Foreigners' Registration Office, Kazi Road, Ganngtok (Tel. 03592-223041) or from the police station at Mangan, Gyalshing or Namchi The Inner Line Permit allows travels in Southern Sikkim and great parts of Eastern and Western Sikkim with the exception of treks in high mountain areas.
For the border regions, e.g. Tsomogo Lake in East Sikkim, most parts of North Sikkim and treks into high mountain regions, including Dzongri and Singalila Ridge a Protected Area Permit (PAP) is required. Foreigners must visit these regions in groups of at least 2 persons accompanied by a representative of an officially acknowledged tour operator. The agency will also apply for the Protected Area Permits.
Certain regions, e.g. Nathu La in East Sikkim or Gurudongman Lake in North Sikkim, cannot be visited by foreigners.