ATMs are widely available, and credit cards are accepted by most businesses, although not everywhere can handle overseas cards, so carry local currency too.
ATMs that accept foreign cards are reasonably common: usually among a row of three or four in a bank at least one will have a ‘Global ATM’ sign or the logo of your credit-card company. Note that convenience store ATMs tend not to accept foreign cards. Restrictions on the amount you can withdraw vary from place to place.
Many banks in Seoul offer a foreign-exchange service. There are also licensed moneychangers, particularly in Itaewon, that keep longer hours than the banks and provide a faster service, but may only exchange US dollars.
Hotels, shops and restaurants accept foreign credit cards, but plenty of places, including budget accommodation and stalls, require cash.
The South Korean unit of currency is the won (₩), with ₩10, ₩50, ₩100 and ₩500 coins. Notes come in denominations of ₩1000, ₩5000, ₩10,000 and ₩50,000.
Tipping is not required nor expected in South Korea.