You can enhance the standard offering of CRM fields so that they can be used inside the ICM engine for your organization's specific requirements. You do this in Customizing in CRM, by choosing:  Customer Relationship Management Incentive and Commission Management CRM-ICM Transfer of CRM Documents to ICM ICM Engine General Settings Maintain Fields for Customer Enhancement of Transfer .

After you have established your organization's specific requirements to ICM in ERP, you will need to do the same in CRM. You do this in Customizing in CRM, by choosing:  Customer Relationship Management Incentive and Commission Management CRM-ICM Transfer of CRM Documents to ICM CRM - General Settings Maintain Fields for Customer Enhancement of Transfer .