I have created 4 custom field in contact named

• x_pos_code

• x_ers_no

• x_owner_name

• x_activation_date

These fields are showing correctly in the contact. Now I am having a problem showing it in the invoice. For example, From invoice, when I am selecting the customer from the drop-down,   Delivery Address is auto-populated. I want to show two more field there x_pos_code & x_ers_no. So that when I search all other fields are auto-populated. I found the line of code. 

<field string="Customer" name="partner_id" context="{'search_default_customer':1, 'show_address': 1, 'show_x_pos_code': 1, 'default_company_type': 'company'}" options="{"always_reload": True, "no_quick_create": True}" domain="[('customer', '=', True)]"/>

I have added this 'show_x_pos_code': 1, but it is not working. May be I am doing it wrong.

What is the correct way to do that?