eiru_hide_Tax/views/sale_view.xml

<?xml version="1.0" encoding="UTF-8"?>
<openerp>
    <data>
        <record model="ir.ui.view" id="sale_order_inherit">
            <field name="name">sale.order.inherit</field>
            <field name="model">sale.order</field>
            <field name="inherit_id" ref="sale.view_order_form"/>
            <field name="arch" type="xml">
                <data>
                    <xpath expr="//field[@name='amount_untaxed']" position="attributes">
                        <attribute name="string">Subtotal</attribute>
                    </xpath>
                    
                    <xpath expr="//field[@name='amount_tax']" position="attributes">
                        <attribute name="invisible">1</attribute>
                    </xpath>
                    
                    <xpath expr="//field[@name='tax_id']" position="attributes">
                        <attribute name="invisible">True</attribute>
                    </xpath>
                    <xpath expr="//tree/field[@name='tax_id']" position="attributes">
                        <attribute name="invisible">True</attribute>
                    </xpath>
                </data>
            </field>
        </record>

        <template id="sale_tax_hide" inherit_id="sale.report_saleorder_document">
            <xpath expr="//table/thead/tr/th[2]" position="replace"/>
            <xpath expr="//table/tbody/tr/td[2]" position="replace"/>
            <xpath expr="//div/div/table/tr[2]" position="replace"/>
            <xpath expr="//div/div/table/tr[1]" position="replace"/>
        </template>
    </data>
</openerp>