Regarding Scheduling Agreement Collaboration, in which planning horizon zone are suppliers allowed to create a...

Suppliers are allowed to create a Ship Notice in theFirm Zoneof the planning horizon in Scheduling Agreement Collaboration. The Firm Zone represents the committed portion of the schedule, where changes are not expected and orders are considered confirmed.

Other Zones:

Committed Zone: Specific to supplier commitments.

Trade-off Zone: Allows adjustments with negotiated penalties.

Planning Zone: Involves forecasts and tentative plans.

Further details are outlined in SAP documentation:Planning Horizon Zones