You are required to have a valid visa to enter Bhutan. The Bhutanese Embassies abroad do not issue visas, and Visa on arrival is non-existent. Therefore, it is to get a visa for Bhutan before arriving.
You must submit a scanned copy of your passport details four weeks before your arrival date. Then, your travel company will process your application and provide you with a copy of the Visa. It usually takes 2-3 working days to approve the application.
You need to have a valid passport for at least six months beyond the length of your stay.
The Visa fee is US$40, and the Tourism Development Fund (TDF) is US$10. These fees need to be sent together with the tour payment.