All visitors coming to Bhutan require a visa except those from India. You are required to pay the Sustainable Development Fee (SDF) of US$100 per day, which is 50% concession from initially approved rate and concessionary rates apply for children. A non-refundable, visa application fee of US$ 40 is also payable. For Indian nationals, no visa is required but the SDF is Rs. 1,200 per day per person. However, you are required to obtain a permit either at the entry point or before your arrival.
The SDF is exclusive of your hotel accommodation, vehicle hiring charges, food and beverage bills, entry fees to monuments and guide fees.
You can apply for visa online here..To apply for a visa online you will need:

1. A digital copy of a valid passport

2. A recent digital passport photo

3. Arrival and departure dates 

4. Valid travel insurance for the duration of your travel 

5. Payment details

 
For Indian nationals you can apply for your permit here (Visit Bhutan - Kingdom of Bhutan (doi.gov.bt).
If you have booked your travel with a tour operator, they can apply on your behalf. No fees are payable in advance. 

Arrive by air

Bhutan has two national airlines: Drukair and Bhutan Airlines. Direct flights to and from international airport in Paro connect you to Bangladesh (Dhaka), India (Bagdora, Gawahati, Kolkata and New Delhi), Nepal (Kathmandu), Singapore, and Thailand (Bangkok).

Arrive by road

There are four official entry points by road from India: Samtse and Phuentsholing (in western Bhutan), Gelephu (in central Bhutan), and Samdrup Jongkhar (in eastern Bhutan).

Local Transport

The most convenient way to travel in Bhutan is to hire a vehicle and driver from a car rental company or a tourism service provider.
Guests can also bring their own cars paying a charge of Nu 4,500 per day for a car. However, there is a mandatory requirement of a guide. The cars must meet the requirements of Bhutan's Roads Safety and Transport Authority, insurance documentation, pollution control documentation, an entry permit, and the driver must also have a valid driver's license. A valid Indian driver's license is accepted for self-driving within Bhutan. The same fees and rules apply for motorbikes.
In case the vehicle is not owned by the guests travelling to Bhutan, an authorization letter is required.
Four airports, Paro International Airport in the west, Yonphula in the East, Bumthang in central and Gelephu in the south connects the country to all regional hubs.
The Royal Bhutan Helicopter Services Limited (RBHSL) is available for private hire. It also offers heli-hiking and other guest services. Helicopters only fly in clear and calm weather conditions.