The official currency in Cambodia is the riel (KHR), there are only notes in denominations of 100, 500, 1000, 2000, 5000, 10,000, 20,000, 50,000 and 100,000 riels (cuts 50 000 and 100 000 are quite rare). The second currency is the U.S. dollar ($) there are notes of 1 to 100 U.S. dollars, the coins are not used in Cambodia.
Currency in which the payments?
Most purchases will be made in U.S. dollars due to the low value of material about 4,000 riels for one dollar, the Cambodian authorities use the dollar for the payment of the tourist visa, it is better to change a minimum of moneys dollars before arriving, the Cambodian riel are mostly used as currency in the big cities of Cambodia, however if you go find non tourist provinces it is advisable to bring this riels.
Where change money and in what currency?
The exchange rate in Cambodia is better than in the offices of Western currency, to get the best exchange rate, go change your euros or other currencies in small exchange offices located around the markets in general. Change your money in dollars and a small amount in riels to pay your small fee, because it is sometimes difficult to make money in small businesses.
Credit cards in Cambodia.
You can find ATMs that accept Visa card or Mastercard in all major cities. It is rare that businesses have a system of payment by credit card in Cambodia, it is best to always have cash on either.