Rollover Data is a feature provided on mobile data plans. Mobile data plans which are sold in fixed amounts of data per month, for example, 10MB of data, grant the subscriber up to this amout of data for consumption within a billing cycle.
At the end of the billing cycle, data balance that is not used is forfeited. Rollover data allows the unused balanced at the end of the billing cycle to be brought forward into subsequent months, subject to terms of the rollover data program offered by a mobile network operator.