The Due Date is referring to the final date that the you, the organization, can submit an applicable rebuttal for the reason for your challenge.  Ideally, this rebuttal should be done at the time you challenge the chargeback.  If you did not submit your rebuttal information at the time you challenged the chargeback, you can email with the case number that appears in the portal for that chargeback (the very first field in the 'Under Dispute' section) to provide your applicable rebuttal. 

It is extremely important that you take action with all chargebacks in a timely manner, whether you are challenging or accepting them. We recommend signing up for the email notification for chargebacks so that someone at your organization is aware an action is required.