Credit Cards have limited acceptability and payment through credit card is accepted mainly by Deluxe hotels and few selected Handicrafts establishments only.
There are ATMs in Bhutan but currently they only operate with their respective Bhutanese banks.
Since these ATMs currently do not function with outside banks, so ATM facility can not be used by visitors. Traveler's checks / cash are best option if you need additional money.
Cash and Travelers Cheques exchange facility is available for most of the main currencies including the US dollar, Euro, Indian Rupee, Japanese Yen, Thai Baht, Pound Sterling, Swiss Franc, Hong Kong dollar, Canadian dollar, Australian dollar, Singapore dollar, Danish kroner, Norwegian kroner, and Swedish kroner. Exchange rates vary.
It is also possible to have funds wired with the services of Western Union but funds cannot be accessed in all locations, and are limited in amounts and days of availability.