Visa can be obtained on arrival at the Tribhuvan International Airport,, Kathmandu, at border entry points in Kakadvitta, Birgunj, Bhairahawa, Nepalgunj, Gaddachowki on Nepal-India border and Kodari on Nepal-China border. Visa can also be obtained at the nearest Nepal Embassy or Diplomatic Mission. Visa can also be obtained (renewal purposes) at Department of Immigration, Kalikasthan, Kathmandu. A valid passport and one passport -size photo with a light background is required. Immigration Department has not specified the size of the passport-size photo. Visa can be obtained only through payment of cash in the following currency: Euro, Swiss Franc, Pound Sterling, US Dollar, Australian Dollar, Canadian Dollar, Hong Kong Dollar, Singapore Dollar and Japanese Yen. Credit card, Indian currency and Nepali currency are not accepted as payment of visa fee.

You can also apply for visa online, follow below link -
http://online.nepalimmigration.gov.np/tourist-visa

a) Tourist Visa

Visa Facility	Duration
Multiple entry	15 days
Multiple entry	30 days
Multiple entry	90 days

b) Gratis (Free) Visa

• For first visit in one visa year (January to December), gratis visa for 30 days is available only for nationals of South   Asian countries like Bangladesh, Bhutan, Maldives, Pakistan and Sri Lanka. However, visa can be extended from the Immigration Department on payment of visa fee as specified above.
• Indian nationals do not require visa to enter into Nepal. 

c) For Indian National
Indian nationals do not require visa to enter Nepal.
As per the Nepalese Immigration, Indian Nationals Traveling to Nepal must possess any One of the following documents.

1. Passport
   
2. Driving License with photo
   
3. Photo Identity card issued by a Government Agency
   
4. Ration Card with Photo
   
5. Election Commission Card with Photo
   
6. Identity Card issued by Embassy of India in Kathmandu
   
7. Identity Card with Photo issued by Sub- Divisional Magistrate or any other officials above his rank

Also, please check with your nearest travel agents for documents required by the Indian Immigration for Indians traveling to Nepal.

d) Other Information
Nationals from Nigeria, Ghana, Zimbabwe, Swaziland, Cameroon, Somalia, Liberia, Ethiopia, Iraq, Palestine and Afghanistan will need to obtain visa from Nepal Embassies or Diplomatic Missions in their respective countries, as they do not get visa on arrival at the immigration entry points of Nepal.

e) Visa Extension
Tourists can stay for a maximum of150 days in a visa year (Jan 1 to Dec 31).