The Malaysian currency is the ringgit, informally known as the dollar and abbreviated RM or MYR, is divided into 100 sen. There are coins of 5, 10, 20, and 50 sen as well as bills of RM1, 2 (rare), 5, 10, 50 and 100. 5 sen coins are mainly given as change in large establishments and supermarkets; street vendors might be reluctant to accept them. Note that the Singapore and Brunei dollars are also known as ringgit in Malay, so when near border areas you might want to check to be sure which currency they are quoting the price in.
Ringgits are freely convertible. Foreign currencies are not generally accepted, although you might get away with exchanging some Euros or US dollars even in more remote areas, but do expect a lot of stares and some persuasion. The major exception is Singapore dollars, which are accepted by KTMB and toll roads, but at a highly unfavourable 1:1 exchange rate (an anomaly dating back to when the ringgit was interchangeable with the Singapore dollar, prior to the 1970s).
All commercial banks are authorised foreign exchange dealers; major hotels are only licensed to buy or accept foreign currency in the form of notes and traveller's checks. Licensed money changers in major shopping malls often have the best rates – be sure to say the amount you wish to exchange and ask for the 'best quote' as rates displayed on the board are often negotiable, especially for larger amounts. It may be difficult to exchange foreign currencies outside the main tourist centres.
ATMs are widely available in cities, but do stock up on cash if heading out into the smaller islands or the jungle. Credit cards can be used in most shops, restaurants and hotels.
The import and export of local currency is limited to RM1,000 cash. There are no restrictions on the import and export of foreign currency, subject to declarations for amounts of $10,000 or higher.