In general, What is the best way to migrate Quickbooks transactions into Netsuite? I can’t find much information about it. Is it like importing Sales Orders by csv? If it’s invoices, then are they treated a certain way to not post to ledger or balances?

@Michael McNamara importing historical sales transactions as closed sales orders will prevent the transaction from posting to the ledger. The trick is converting the QB file to an importable NetSuite file. I have a tool that can quickly do this if you are interested in learning more.