Only the local currency, the Nepalese Rupee, is accepted in Nepal. So, the foreign currency must be exchanged. Thankfully, the process is quite easy. Most urban cities have several exchange centers. You can find many of them in Kathmandu and Pokhara. Airports and banks also exchange foreign currency. Although foreign currencies can be accessed directly through ATMs, it is not recommended. This is because it might not be accepted. Even if accepted, you might not get a good exchange rate.
Banks in Nepal remain open from 10:00 am to 4:00 pm, Sunday to Thursday, and from 10:00 am to 3:30 pm on Friday. Head offices of many banks remain open till 5:00 pm. Some Banks in Thamel, Kathmandu are open till a late hour. However, commercial exchange counters may give you a better rate. Only hotels and restaurants in urban areas like Kathmandu accept credit cards and Traveler's Cheques. Traveler's Cheques can be carried in Pounds Sterling or US Dollars.
Can I change money, or are there ATMs while trekking?
You can exchange money at the many exchange centers in Kathmandu and Pokhara. ATMs are present only in Kathmandu and Syabrubesi.