A visa is necessary to enter in Nepal and can be obtained for the following duration from the entry point of Nepal or Royal Nepalese embassy or consulate in your country. Require two passport size photos.
Tourist visa:

Visa year 15 days for multiple entry	US $ 25
Visit in the visa year 30 days for multiple entry	US $ 40
Visit in the visa year 100 days for multiple entry	US $ 100
Transit or gratitude visa for 3 days	-
Fee exemption children below 10 years	-

Note: Reentry facilities should be used within the validity of the visa period. It is not considered as a visa extension.
Business visa: Business visa with multiple entry facilities for the period of one year and five years can be obtained on the recommendation of Ministry of Industry by paying the equivalent of US$ 100 and US$ 250 respectively.
Arrival: Tourist arriving at Tribhuvan International Airport in Kathmandu with out any dutiable goods can proceed through the green channel for quick clearance with out a baggage check. If you are carrying dutiable articles, you have to pass through the Red channel for detailed customs clearance.
Airport departure tax: Passengers service charge and Tourism service fee (airport tax) who are departing from the Tribhuvan International Airport (TIA) are required to pay an airport tax   for SARC nations  RS 1356 (795 + 565) = US $ 20 approx. Apart from SARC Nations RS 1695 ( 1130 + 565 ) = US $ 25 approx.