pos/pos_cash_move_reason/wizard/pos_box.xml

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

    <record model="ir.ui.view" id="cash_box_in_form">
        <field name="model">cash.box.in</field>
        <field name="inherit_id" ref="account.cash_box_in_form" />
        <field name="arch" type="xml">
            <xpath expr="//field[@name='name']" position="before">
                <field name="product_id" required="1" class="oe_inline"
                    domain="[('income_pdt', '=', True)]"/>
            </xpath>
        </field>
    </record>

    <record model="ir.ui.view" id="cash_box_out_form">
        <field name="model">cash.box.out</field>
        <field name="inherit_id" ref="account.cash_box_out_form" />
        <field name="arch" type="xml">
            <xpath expr="//field[@name='name']" position="before">
                <field name="product_id" required="1" class="oe_inline"
                    domain="[('expense_pdt', '=', True)]"/>
            </xpath>
        </field>
    </record>

</data></openerp>