How to generate Single Invoice from Many Sales Orders

Natively, NetSuite does not allow you to bill multiple Sales Orders on one Invoice. There are a couple of options you could explore as alternative approaches:

1. If you have SuiteBilling you can use Consolidated Billings. See Suite Answer 9204: Using Consolidated Billing for Projects and for Payments
2. You could leverage Group Invoicing which might help facilitate a better experience for your customers without breaking the 3-way matching that invoicing individual Sales Orders provides.