Taxis (actually large vans) in Providenciales are metered, and rates are regulated by the government at $2 per person per mile traveled. In Provo call the Provo Taxi & Bus Group for more information. In the family islands, taxis may not be metered, so it's usually best to try to negotiate a cost for your trip in advance.
Provo Taxi & Bus Group (649/946-5481).