account_invoice_view.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>

    	 <record model="ir.ui.view" id="invoice_supplier_form">
    	     <field name="name">account.invoice.supplier.form</field>
    	     <field name="model">account.invoice</field>
    	     <field name="inherit_id" ref="account.invoice_supplier_form"/>
    	     <field name="arch" type="xml">
    	     	<xpath expr="//field[@name='journal_id']" position="after">
    	     		<field name="customs_doc_type" attrs="{'readonly': ['|',('state', '!=', 'draft'), ('forwarder_bill_of_entry_ids', '!=', [])]}"/>
	     		</xpath>
    	     	<xpath expr="//notebook/page[@string='Payments']" position="after">
    	     		<page string="Customs" attrs="{'invisible': [('customs_doc_type','=', False)]}">
    	     			<separator string="Bill of entries" colspan="4" attrs="{'invisible': [('customs_doc_type','!=', 'supplier_invoice')]}"></separator>
                        <field name="supplier_bill_of_entry_ids" attrs="{'invisible': [('customs_doc_type','!=', 'supplier_invoice')]}" />
    	     			<separator string="Supplier invoices" colspan="4" attrs="{'invisible': [('customs_doc_type','!=', 'bill_of_entry')]}"></separator>
    	     			<field name="supplier_invoice_ids" attrs="{'invisible': [('customs_doc_type','!=', 'bill_of_entry')]}" domain="[('customs_doc_type', '=', 'supplier_invoice')]" context="{'default_customs_doc_type': 'supplier_invoice'}"/>
                        <group>
                            <field name="forwarder_invoice_id" attrs="{'invisible': [('customs_doc_type','!=', 'bill_of_entry')]}" domain="[('customs_doc_type','=', 'forwarder_invoice')]" context="{'default_customs_doc_type': 'forwarder_invoice'}"/>
                        </group>
    	     			<separator string="Bill of entries" colspan="4" attrs="{'invisible': [('customs_doc_type','!=', 'forwarder_invoice')]}"></separator>
    	     			<field name="forwarder_bill_of_entry_ids" attrs="{'invisible': [('customs_doc_type','!=', 'forwarder_invoice')]}"/>
    	     			<group>
                            <field name="bill_of_entry_storno_id" attrs="{'invisible': [('customs_doc_type','!=', 'forwarder_invoice')]}"/>
                        </group>
                        <button string="Make Bill of Entry" name="%(account_invoice_template.action_wizard_select_template)d" type="action" class="oe_highlight" attrs="{'invisible': ['|',('customs_doc_type','!=', 'forwarder_invoice'),('state','!=','draft')]}"/>
    	             </page>
    	         </xpath>
                <xpath expr="//notebook/page[@string='Invoice']/field[@name='invoice_line']/tree/field[@name='price_subtotal']" position="after">
                    <!--It seems attrs doesn't work -->
                    <field name="advance_customs_vat"/>
                </xpath>
    	     </field>
    	</record>
    <record model="ir.ui.view" id="invoice_form_boe">
      <field name="name">account.invoice.form.boe</field>
      <field name="model">account.invoice.line</field>
      <field name="inherit_id" ref="account.view_invoice_line_form"/>
      <field name="arch" type="xml">
        <field name="name" position="after">
          <group>
          <field name="advance_customs_vat"/>
          </group>
        </field>
      </field>
    </record>

	</data>
</openerp>