Cambodia uses both the riel (KHR) and the US dollar (USD). Prices are often quoted in USD, and change may be given in riel (around 4,000 riel per 1 USD). Bring clean USD notes and some riel for small spending such as tuk-tuks and markets. Torn, stained or heavily creased USD notes are often refused, so check each note.
ATMs: most dispense USD only. Each withdrawal usually costs about 5 to 10 USD in fees, with limits of roughly 500 to 2,000 USD per transaction depending on the bank, so withdrawing once in a larger amount is better than several small withdrawals.
Cards: Visa and Mastercard work at larger hotels, restaurants and supermarkets in Phnom Penh and Siem Reap; some places add a surcharge of about 5%. Markets and small shops are often cash only.
QR: Cambodia uses KHQR. Foreign visitors can use the Bakong Tourist wallet from the National Bank of Cambodia to scan KHQR without a bank account; it needs identity verification and a prepaid balance. It is optional, and some users report card-linking problems. After scanning, check the merchant name and the amount.