You want to create a Sales Order with an Invoice Schedule for an Item via the web service ManageSalesOrderIn.
SAP Business ByDesign
The Invoice Schedule is currently not supported in the standard Sales Order web service API and also not via oData.
You can only add an Invoice Schedules manually in a Sales Order.
Invoice Schedule; web service; OData , KBA , SRD-CRM-ORD , Orders & Contracts , Problem