The local currency is the Riel. US$1.00 = 4100 Riel .Notes comes in denominations of 100, 200, 500, 1,000, 2,000, 5,000, 10,000. Coins are no longer used. However, US$ are widely accepted and easily exchanged across the country. In Phnom Penh and other towns most goods and services are priced  in dollars and there is a little need to buy riel.  In remote rural areas prices are quoted in riel (except accommodation).

In western districts, particularly Poipet,  Pailin and Koh Kong the  Thai Baht is widely used.

Credit cards and travelers checks are accepted at most upscale hotels, shops and restaurants, some mid-range place and a growing number of other businesses. Credit cards are general not accepted at any businesses outside of Phnom Penh, Siem Reap, Sihanoukville and the casinos in Poipet. The most commonly accepted credit card is Visa Card. MasterCard and JCB are growing in popularity. A few places accept AMEX. Most businesses charge a 2%-4% fee to accept credit cards.
AMEX in US dollars are the most widely accepted travelers checks. ‘Instant’ cash transfers can be done through MoneyGram or Western Union.
There are banks in all of the larger provincial capitals, including Phnom Penh, Siem Reap, Sihanoukville, Kampot and Battambang. Banks offer cash advances on credits cards (most accept Visa card), change money, telegraphic transfers, cash travelers checks and ANZ Royal Banks offer ATMs with international access.
ANZ Royal Bank ATMs with international access are available at several locations in Phnom Penh, Siem Reap and Sihanoukville. Accepting Maestro, Cirrus, Visa Plus, Visa and MasterCard. Dispenses US dollars.

Money changers offer a slightly better rate that the banks. They tend to cluster around the traditional markets. There is usually a section of a traditional market dedicated to moneychangers and gold sellers.