We need to pass the Internal Id of the Billing Schedule to NetSuite while creating the Sales Order either through Custom URL or Global API. In NetSuite, you can find the Billing Schedule's Internal Id from here: Lists > Accounting > Billing Schedules > New. Here is an example of the billing schedule.
Once you have the Internal Id of a Billing Schedule record, you can pass it to Breadwinner either as a field that contains the Internal ID or as raw data within the Custom URL itself without creating any fields (only an appropriate choice if you always use the same value).
At the transaction level:
At the line item level:
Note: The billing schedule is shown on the line items only when forms are customized in NetSuite to show schedules on lines.