Indian citizens do not have any entry formality to visit Sikkim. However, there are certain areas like Tsomgo Lake, Nathu la, Dzongri etc which are defined as 'Protected Areas' having special army deployment and Indian citizens also require a separate permit known as 'Protected Area Permit' (PAP) to visit such places.
Indian citizens need to carry a Photo ID proof like passport, Voter's ID card, Driving License etc. for issuance of Protected Area Permit (Note: PAN card is not accepted).
Based on your place of visit, here is how you can get the Protected Area Permits:
East Sikkim
Tsomgo (Changu) Lake and Baba Mandir permits are issued at the Police Check Post. Most convenient is to apply through Travel Company like us who is doing your travel arrangements.
Permit for Nathu la can be obtained from Police Check Post as well as Sikkim Tourism Department Office while if the tour is booked through our office then we can process and obtain this permit in advance.
West Sikkim
Dzongri, Goecahala Trek, Singalila Trek: Permit is issued by the Adventure Cell of Sikkim Tourism & Civil Aviation Department. while if the tour is booked through our office then we can process and obtain this permit in advance.
North Sikkim
Yumthang, Yumesamdong, Thangu / Chopta Valley: Permit is issued by the Tourism Department and Police Check Post. While we as Tour Operator can process and obtain permit in advance if the tour is booked with us.
Gurudongmar Lake: Indians citizen can get the permit at Police Check Post. While we as Tour Operator can process and obtain permit in advance if the tour is booked with us.
South Sikkim
Namchi, Ravangla: No permit is required by Indians citizens.