In the cities and towns, major restaurants, and larger shops will accept credit card but not by small establishment. Once you are out of the cities, you will need cash almost always. There may be few places along the popular trail that may accept credit cards but it is rare. However there are ATMS in many larger villages on the treks. It is best to change the currency in local Nepali Rupees before you go to the trekking in the mountain region, as ATMS are subject to network issues.