All foreign nationals except Indians need a visa to enter Nepal. Tourist visas are issued on arrival with a minimum of fuss at the Kathmandu airport and at official overland entry points. Have a passport-size photo at the ready, and if possible bring exact change for the visa fee - in US dollars if you're entering by air.
Fees may change without warning, but visas currently cost US$15 (or equivalent in other currencies) for fifteen days, $25 for thirty days ($40 for a double-entry visa), and $60 for a sixty-day multiple-entry visa. If you plan on border-hopping between Nepal and India (or Tibet), the double- or multiple-entry option may save some time and money, but it's not essential as you can get a re-entry stamp at any official border crossing (same prices as visas).
Getting a visa from an overseas Nepalese embassy or consulate will cut down on paperwork on arrival, but it's really only worth doing if you happen to be in the neighbourhood or if you're one of those people who has to have everything sorted out before you go. The fees are supposed to be the same as those given above, but are actually often higher.
Tourist visas can be extended , up to thirty days at a time, for a maximum of 120 days in a calendar year (150 days given extenuating circumstances). Extensions are granted only at the Kathmandu or Pokhara Central Immigration offices - a somewhat tedious procedure, especially in high season, when queues can run to two hours or more, which is why it's best to get the longest visa you think you'll need right from the start. The cost is US$1 per day, payable in Nepalese currency only. Submit your passport and one passport-size photo with your application; instant photos are available from studios near Central Immigration offices.
