Sales Order Import Problem

I tried to import a new sales order. There was an error saying the customer is not found. What I try to do was to import lots of past sales orders into the system. Does ERPNext allow me to import orders when the customer or item code not created yet at time of import?

Thanks,
Richard

@Richard_Luil, do you need import first all referenced data by the invoice, like the Customer, Items.

No ERPNext dont allow you to create Invoices without these data, since the ERP, need much more information about the customer, or item, not only the code.