Rebate processing involves creating rebate agreements with customers based on sales volume over a period of time. The standard system includes several rebate types like group, material, and customer rebates. Settings must be activated in the sales organization, billing document type, and customer master to enable rebate processing. Customizing includes defining condition types, agreement types, and assigning these to pricing procedures. Rebate amounts accrue over time and can be settled partially or fully through credit memos that increase or decrease the accrual balance.