suite/l10n_us_mt_hr_payroll/views/hr_payroll_views.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <data>
        <record id="hr_contract_form_l10n_us_mt_inherit" model="ir.ui.view">
            <field name="name">hr.contract.form.inherit</field>
            <field name="model">hr.contract</field>
            <field name="priority">139</field>
            <field name="inherit_id" ref="hr_contract.hr_contract_view_form"/>
            <field name="arch" type="xml">
            <data>
                <xpath expr="//group[@name='state_filing']" position="inside">
                    <group string="Montana" name="mt">
                        <field name="mt_mw4_exemptions" string="Exceptions"/>
                        <field name="mt_mw4_additional_withholding" string="Additional Withholding"/>
                        <field name="mt_mw4_exempt" string="Withholding Exempt Reason"/>
                    </group>
                </xpath>
            </data>
            </field>
        </record>
    </data>
</odoo>