There is no id problem we are passing correct id,  the problem is that supplementary_allowance is an inherited view of odoo so we are not able to go to correct xpath, so kindly provide correct xpath if you know. Thanks 

I think external id is not found error in your code.please refer my code

<record id="hr_contract_form_hides_supp_allow" model="ir.ui.view">

            <field name="name">hr.contract.view.form.hides.supp.allo</field>

            <field name="model">hr.contract</field>

            <field name="inherit_id" ref="hr_contract.hr_contract_form_inherit"/>

            <field name="arch" type="xml">

                <xpath expr="//field[@name='supplementary_allowance']" position="attributes">

                    <attribute name="invisible">1</attribute>

                </xpath>

            </field>

</record>