The currency in Bali is the Indonesian Rupiah [ru-pee-ah], also known as Rp.
Cash is still used widely in Bali so make sure you keep some on you, especially for markets, smaller shops, transport and food and drink, as not all places take card. Even when they do, their card machine may well not be working so it’s always a good idea to check with them first.
Tipping staff in hotels and restaurants is also done with cash.
Consider keeping a stash of notes under 100,000, especially when making purchases at markets or smaller shops as merchants will often struggle to make change. The best notes for these places are 50,000 and 20,000 unless you’re planning on buying something very expensive or a lot of things from one place.