account_payment_term_extension/account_view.xml

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

        <record id="view_payment_term_line_form" model="ir.ui.view">
            <field name="name">account.payment.term.line.form.extension</field>
            <field name="model">account.payment.term.line</field>
            <field name="inherit_id" ref="account.view_payment_term_line_form"/>
            <field name="arch" type="xml">
                <div attrs="{'invisible':[('value','=','balance')]}" position="after">
                    <field name="amount_round"
                        attrs="{'invisible':[('value','=','balance')]}"/>
                </div>
                <field name="days" position="after">
                    <field name="weeks"/>
                    <field name="months"/>
                </field>
                <field name="days" position="before">
                    <field name="start_with_end_month"/>
                </field>
            </field>
        </record>

        <record id="view_payment_term_line_tree" model="ir.ui.view">
            <field name="name">account.payment.term.line.tree.extension</field>
            <field name="model">account.payment.term.line</field>
            <field name="inherit_id" ref="account.view_payment_term_line_tree" />
            <field name="arch"  type="xml">
                <field name="value_amount" position="after">
                    <field name="amount_round"/>
                </field>
                <field name="days" position="after">
                    <field name="weeks"/>
                    <field name="months"/>
                </field>
                <field name="days" position="before">
                    <field name="start_with_end_month"/>
                </field>
            </field>
        </record>

    </data>
</openerp>