As Tibet is part of China, obviously the currency used here is Chinese "Yuan" or "Kuai"- the officially called Renminbi (RMB) which means "People's money". It's designated by a “Y.” The banknotes come in the denomination of 1, 2, 5, 10, 20, 50 and 100 where the largest denomination used in daily life is the 100 Yuan note.
US Dollars and Euros are widely accepted by hotels and large businesses. Small businesses do not accept foreign currency and so you need to exchange them in Bank of China and its branches at Gonggar Airport, at Lhasa and Shigatse. Although Travelers Checks are also accepted in the Bank of China and a few hotels, it's use has declined in the recent years and so it's advisable not to bring traveler checks.
There are several ATM machines in Lhasa and Shigatse. The maximum amount you can withdraw is around 2000 Yuan in one transaction. Few shops and agencies do accept credit cards and often charge a 4% surcharge and the Lhasa central branch of the Bank of China is the only place in Tibet that provides cash advances on a credit card with 3% commission is deducted. In Lhasa, most of the internationally accepted credit cards are usable including Visa, MasterCard, Diner's club, and the JCB card of Japan. AmEx cards are not so popular. Credit cards are accepted only in large shopping stores and hotels while small vendors prefer to deal in cash. Those hotels and shops who accept credit card, symbols are displayed in the visible place to indicate. Please make sure that before departure, you confirm with your bank if your credit cards and debit cards work in China and if the codes will be the same.