Passports:
Valid passport for a minimum of six months required by all nationals.

Tourist visa:

The foreign tourist visiting Nepal shall be granted the tourist visa.
The tourist visa shall be granted for a period in maximum of 150 days in a visa year (Visa years means January to December).
A tourist who has departed before the expiry of the period specified in the visa issued in a visa year shall not be allowed to use the visa by adding the remaining period to another visa year.
If any foreigner who has entered into Nepal towards the end of a visa year desires to spend even the period during which he may stay in Nepal with the tourist visa of the other visa year, he may use such facility.
Provided, however, that the computation of the fees for such period shall be made on the basis of the total period of his stay.

An application for the tourist visa has to be submitted in the format as referred to in Appendix 1.
Transit Visa:

Foreigners, who have entered In Nepal to stay for a night in Nepal and willing to use Nepal’s Air port to visit another country with plane ticket or Foreigners, traveling in the accidentally force landed plane for any circumstances shall be issued transit visa for one day.
An application for the transit visa has to be submitted in the format as referred to in Appendix 3.
Types and costs:
The fee for a Single Entry Tourist Visa to Nepal for 60 days is US $60 or equivalent foreign currency
Additional $50 grants Multiple Entry Visas
Tourist visa can be extended for a maximum of 150 days. Visa extension free for 30 days is US $ 30
Validity:

Visas are valid for up to six months from date of issue. Visas are valid for 60 days on first visit to Nepal in a visa year (1 January-31 December), but only valid for 30 days when national is visiting Nepal for the second or more time in a visa year. Visas may be extended in Nepal at the Department of Immigration, Kathmandu (tel: 494 273 or 337), or the Immigration Office, Pokhara. Maximum stay in Nepal is 150 days in any calendar year. For full conditions on visa extension (including charges and conditions), contact the consulate (or consular section at embassy); see Important Addresses.

Application to:
Consulate (or consular section at embassy). Visas can also be obtained on arrival from the immigration authorities at all entry points (with fees payable in US Dollars) provided travelers are in possession of valid travel documents, two passport photos and the relevant fee. Applications for business visas must be made to the Department of Immigration

Working days required:
Minimum 24 hours if applying in person; two weeks if applying by post.

Extension of Stay:
A tourist visa can be extended from the Department of Immigration and Pokhara Immigration Office for a total of 120 days. An additional 30 days visa may be granted on reasonable grounds from the department. Over the course of a visa year, a tourist cannot stay in Nepal more than cumulative 150 days.