Can a member still particpate after survey closure?

Our contract is with your organization. This contract allows you to define opening dates, closing dates, buffer periods and results dates. Once these milestones are achieved the survey is deemed to be completed. However, if you specifically wish for a member to participate in a completed survey this can be arranged but it does involve additional costs above contracted price. These costs are not onerous but we do have to charge for time involved with individual processing of a late participant once we have done what we agreed upon.