eiru_service/views/project_service_budget.xml

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

        <record model="ir.ui.view" id="project_service_task_budget_history">
            <field name="name">project.service.task</field>
            <field name="model">project.service.task</field>
            <field name="inherit_id" ref="eiru_service.project_service_task_form"/>
            <field name="arch" type="xml">
                <xpath expr="//field[@name='user_id']" position="after">
                    <button name="%(action_budget_add)d"
                            type="action" class="oe_button oe_form_button oe_highlight" string="Enviar" context="{'default_task_id': id, 'default_amount':amount_total}" attrs="{'readonly': [('state','!=', 'Preparado')],'invisible': [('approved','=',True)]}"/>
                </xpath>
                <xpath expr="//group[@string='Facturación']" position="after">
                    <group string ="Histórico de presupuestos">
                        <field name="budget_ids" nolabel="1" readonly="1">
                            <tree string="Budget" editable="bottom">
                                <field name="date" string="Fecha"/>
                                <field name="task_id" string="Descripcion"/>
                                <field name="user_id" string="Funcionario"/>
                                <field name="amount" string="Valor"/>
                            </tree>
                        </field>
                    </group>
                </xpath>
            </field>
        </record>
    </data>
</openerp>