All tourists visiting Bhutan, excluding Indian, Bangladeshi and Maldivian passport holders require a visa and must book their holiday through a Bhutanese tour company operator or one of their international partners. Travel in Bhutan require payment of minimum tariff set by the Government of Bhutan that includes basic package trip that includes accommodation, meals, Guide, transfers, tourist taxes, visa fees through the tour operator.
The tour operator processes Bhutan visa and other travel permits and then sends this Pre-Approved Visa upon submission of your payment to the Tourism Council. The actual visa is then stamped on your passport upon arrival at the airport or at the entry point, based on this pre-Approved Visa letter. Bhutan Embassies and Missions abroad does not issue tourist visa.
Visas for Official visits to Bhutan are processed through the Govt. agencies, NGOS, UN organisations or agencies inviting you to Bhutan. These organisation will approach Immigration Department. Similarly the Guest visa for is processed by the host through the Immigration Department and Foreign Ministry.