Rotary International Dues are billed semi-annually. Statements were sent from Rotary International by email recently and are payable upon receipt.
Rotary International bills clubs semi-annually based on membership as of the end of June and then the end of December.
Member changes are made through the District Website (or Club website if the club has a ClubRunner subscription) and that information "rolls up" to 
It is important to pay the invoices promptly to ensure that the Club remains in good standing with RI and will qualify for the Rotary Citation.