Antigua and Barbuda use the Eastern Caribbean dollar (EC$).
US dollars are widely accepted. However, unless rates are posted in US dollars, as is the norm with accommodations, it usually works out better to use EC dollars. If you pay in US dollars you will likely get change in EC dollars.
A 10% service charge is added to most restaurant bills, in which case no tipping is necessary.
ATMs can be found at the airport, Nelson’s Dockyard and around St John’s; they dispense EC dollars.