On a sales order form, if the billing schedule is set at the header level, there can be only one billing schedule for that sales order. If there are multiple projects on the sales order, then each of the projects could have a different billing schedule specified on the project record.
In this case, the header-level billing schedule takes precedence over the project-level billing schedules and is used for all projects. This result can be confusing because the information on the individual projects may not be the same as the billing schedule on the sales order.
Visit SuiteAnswers Article #9365 to read more about Billing and Project Consolidation.