Indian nationals intending to visit Bhutan are required to carry any of the two valid “Travel Document” (a) Valid Indian Passport having validity of minimum 6 months; and/or (b) Voter Identity Card, issued by the Election Commission of India alongwith recent Passport size Photographs. For minor children (below 18 years of age), if not having Passport, the Birth Certificate in original is required. No Visa is required to visit Bhutan.
Indians coming to Bhutan by road are required to obtain an ‘Entry Permit’ on the basis of valid Travel Document from the Immigration office of Royal Government of Bhutan at Phuentsholing, located on the Indo-Bhutan border opposite Jaigaon, West Bengal on any working day (Monday to Friday) from 9am to 5pm (BST).
Similarly, Indians coming by air must possess any one of the above mentioned documents and get the Entry Permit at the Paro International Airport. No fee is required for obtaining Entry Permit. The Entry Permit allows an Indian tourist to visit Thimphu and Paro only. However, any tourist going beyond Thimphu and Paro need to acquire a “Special Area Permit” from the RGoB Immigration office at Thimphu on any working days (Monday to Friday).
As per Regional Immigration office, Phuentsholing, prior Hotel booking is required to obtain Entry Permit. The Phuentsholing border gate normally remains open from 6am to 9pm (BST). Entry Permit is not required for Indian nationals to enter Phuentsholing city.
Source: Consular Services : Information for Indian Tourists