Customer Rebate Calculation Question

I am looking at the rebates module and have a few questions.

  1. Are the rebates calculated per invoice or per the defined period in the schedule?

For example, our sales department wants to setup rebates so that every order that is a full truckload (26 pallets), they receive a rebate. Less than a truckload, no rebate. This is per order, not over time.

If I create a rebate contract based on quantity of 26 pallets, will that calculate per invoice or is it cumulative over the schedule that is setup (one month)?

Thank you - Nina