Cambodia accepts US dollars as currency but there is a big push towards using the local currency Reil. You can use your card in most shops to pay but local streetside shops/restaurants may still take cash only. If you have a visa contactless card, that will also work in some places. 

• QR code payment systems are a big way of life here so worth checking if your bank uses that form of payment on your phone.
• Prices can be quoted in either currency. 
• $1 US is about 4000 riel. If you take cash out of an ATM you may be given riel instead of USD.
• If you bring your own cash please try to keep to smaller US notes ($10, $20) as few places have change for larger bills. 
• Damaged USD are often rejected, so please keep this in mind too and check the change you receive. 
• Tips are appreciated but not necessary, bigger places there ma