Normally banks are open between 09:00 A.M. to 3:00 p.m, Sunday to Friday. On Saturdays and other public holidays, they are open for shorter hours and for cash withdrawals and deposits only (not other services). Some banks operate evening counters( till 6 or 7 Pm) in Kathmandu and Pokhara . So , in general you can assume that banks are open 365 days , in Kathmandu and pokhara ( but not in other cities or small towns).
You are supposed to pay in local currency, called Rupees, in the local market for any shopping and payments. However you must pay in foreign currency for air tickets and for visa charges. Airport departure taxes can be paid in Nepali Rupees.
You can exchange your foreign currency at hotels , at banks or your travel agent can do this for you. Foreign currencies like US Dollar, Euro , Japanese Yen, and British Pound are accepted in hotel , travel agencies, restaurants and other establishments easily. However , other currencies are accepted only at banks and we recommend you not to carry these currencies to avoid inconvenience.
Visa and Master cards are widely accepted in the cities , mostly Kathmandu and Pokhara. Bigger hotels and restaurants accept them but smaller hotels and restaurants will not accept them .
There are ATM machines at several places in Kathmandu, Pokhara and some other cities including some at Kathmandu airport. The credit card service charge is normally 3.5% in Nepal. You can also get Nepali Rupees against travelers cheques at banks.
If you are heading for a trek to the mountains, make sure you have enough Nepali cash for your personal expenses. Some lodges in the mountains may accept US dollars but the exchange rate offered is very low.
If you are traveling via India , you can use your remaining Indian rupees in Neapl . However Indian Rupees of 500 denominations are illegal to carry in Nepal and the authorities may confiscate it at the airport.