All foreigners, except Indians, must have a visa. Nepali embassies and consulates overseas issue visas with no fuss. You can also get one on the spot when you arrive in Nepal, either at Kathmandu's Tribhuvan Airport or at road borders: Nepalganj, Birganj/Raxaul Bazaar, Sunauli, Kakarbhitta, Mahendranagar, Dhangadhi and even the funky Kodari checkpoint on the road to Tibet.
A Nepali visa is valid for entry for three to six months from the date of issue. Children under 10 require a visa but are not charged a visa fee. Your passport must have at least six months validity. Indian nationals do not require a visa. Citizen of South Asian countries and China need visas but these are free.
You can download a visa application form from the websites of the Nepali embassy in Washington, DC (www.nepalembassyusa.org) or London (www.nepembassy.org.uk).
To obtain a visa on arrival by air in Nepal you must fill in an application form and provide a passport photograph. Visa application forms are available on a table in the arrivals hall, though some airlines (like Thai) provide this form on the flight. To get a jump on the immigration queue, you can download the visa-on-arrival form from www.treks.com.np/visa. A single-entry visa valid for 60 days costs US$30. At Kathmandu's Tribhuvan Airport the fee is payable in any major currency but at land borders officials will probably require payment in cash US dollars; bring small bills. Only single-entry visas are routinely available on arrival, though you may be able to score a multiple-entry visa if you ask.
If you have already visited Nepal during the same calendar year the visa fee is the same but you'll only get a 30-day visa. Much of the time you spend in the visa-on-arrival queue is waiting while officers scour your passport for previous entry stamps. It's worth knowing that if you stayed longer than 15 days in Nepal and are planning a second visit within the same calendar year, your second 30-day visa should be free.
At Nepali embassies abroad it's possible to get a multiple-entry visa (US$80 or equivalent), which gives you multiple trips into Nepal for a year, with each stay valid for 60 days, up to a total of 150 days in any calendar year. Multiple-entry visas are useful if you are planning a side trip to Tibet, Bhutan or India. You can change your single-entry visa to a multiple-entry visa at Kathmandu's Central Immigration Office for US$50.
If you are just planning a lightning visit to Kathmandu it's possible to get a free nonextendable three-day transit visa at Kathmandu airport, as long as you have an air ticket out of the country within three days.
If you stay in Nepal for longer than the duration of your initial 60-day visa, you will require a visa extension. Transit visas are nonextendable.
Don't overstay a visa. You can pay a fine of US$2 per day at the airport if you have overstayed less than 30 days (plus in theory US$3 per day between 30 and 90 days and US$5 per day for over 90 days). If you've overstayed more than a week get it all sorted out at Kathmandu's Central Immigration Office before you get to the airport, as a delay could cause you to miss your flight.
It's a good idea to keep a number of passport photos with your passport so they are immediately handy for trekking permits, visa applications and other official documents.
Visa extensions are available from immigration offices in Kathmandu and Pokhara only and cost US$30 (payable in rupees) for a 30-day extension. You get a 30-day extension whether you are staying for an extra day or an extra 30 days. A multiple-entry visa extension costs US$80.
Every visa extension requires your passport, money, photos and an application form. Collect all these before you join the queue. Plenty of places in Kathmandu and Pokhara will make passport photos for you and there are several pricier instant-photo shops near the immigration offices.
Visa extensions are available the same day, sometimes within the hour. For a fee, trekking and travel agencies can assist with the visa extension process and can usually save you the time and tedium of queuing.
You can extend your visa up to a total stay of 120 days without undue formality. You should be able to get a further 30 days extension but you may need to show a flight ticket proving that you are leaving the country during that time period, since you are only allowed to stay in Nepal for a total of 150 days in a calendar year on a tourist visa.