From Sunday 2 December 2018 State Transit Bus Services will become cash free. This includes all services operated by STA, including buses in the Eastern Suburbs, Lower North Shore and Northern Beaches. STA services in the Riverside Suburbs and North West are already cash free.
This will mean that Opal single tickets will no longer be sold onboard any State Transit bus service and passengers must have an Opal Card with sufficient balance in order to travel. This new policy is expected to speed up services and increase reliability by removing delays caused by ticket sales.
Transport NSW Blog 