Inner Line Permits: Foreign Nationals require an Inner Line Permit to enter Sikkim. The said permits are a formality and issued free of cost. You require a valid Indian Visa, passport copy and photos to apply for one. Permits can be obtained easily, upon arrival at Melli police check post or Rangpo border post. Permits can also be obtained at;
Permit Extensions: Permits are generally valid for 30 days (sometimes 15 days from Embassies abroad). These can be extended at the Government offices in Gangtok and Tikjuk (5km below Pelling) for another 30 days allowing a maximum stay of 60 days. Reentry into Sikkim once you exit is three months before you can apply for another permit.
Permit Validity: Inner Line Permit is valid for the following places;
Gangtok, Rumtek and Lingdum
Anywhere in the Gangtok – Singhik Road
Most of West Sikkim where paved roads extend
Special Permits: High altitude treks, including Goecha La and Singalila Ridge routes require trekking permits valid for up to 15 days and organized by trekking agents. Travels beyond Singalila up to Lachung and Lachen Valley require an additional restricted area permit from the tourism and police department which will get you to Tsopta Valley or Yume Samdong (Zero Point) only. Indian nationals require a police permit and can travel further up to Thangu Valley and Gurudongmar Lake. Foreign Nationals also need a restricted area permit to visit Changu Lake. Only Indians are allowed to travel further to Nathula Pass.