I have added a required field in customer attribute named as reference_number. If I create a new customer and save the attribute I am able to create the order for customer . But if i create a order for new customer from backend (which is not in db) it throws the exception or order save as

The value of attribute "Reference No" must be set

I don't know if I have to save the refernce_number using knockout or observer .

In Short order created through these steps throws the Error

Sales->Order->Create New Order->Create New Customer->Submit Order