Besides a Valid Passport a special permit to visit Sikkim. There are how easy to obtain , with all Indian Embassies Consulates and high commissions abroad authorized to Issue a 15 days inner line stamped in to your passport on request when you obtain your Indian Visa. You can also get your 15 days permit from any of the Sikkim tourism Office in Delhi, Kolkata, Siliguri or at Darjeeling. If you find yourself at Sikkim’s border town at Rangpo wit out already having obtained a permit don’t worry , because of Tourism officer stationed on the spot. Regardless of where you apply for you Sikkim permit, you must submit photo copy’s of your passport and Indian Visa details, along with two passport size photographs.
Your initial 15 days permit can be revalidated for 3further instalment of 15 days each in case you wish to stay longer. The 60days, beyond which it is impossible to extend your permit further. The foreigners’ Registration office at Gangtok and the Superintendents of police of North, South and West Districts has the authority of extend permits. With your regular 15 day permit you gain o access to Gangtok , all district head quarters ( Soreng Pakyong, Ravangla) except Chungthang in North Sikkim which is only accessible to foreigners who from a group of two and more . the permit also covers Rumtek , Phodong, Pemayangse, Kheehuperi and Tashiding.
Areas like Tsomgo Lake which is a 3 hours drive from Gangtok , the Youmthang Valley in North Sikkim, and the trekking areas in west Sikkim are open only to group of two or more and require additional special permit. These can be arranged through authorised local travel agents on arrival in Sikkim. However permit to visit North Sikkim is allowed for maximum period of 5 days and 1 day only Tsomgo Lake.