eiru_payments_invoices/views/eiru_payments_invoices.xml

<?xml version="1.0" encoding="UTF-8"?>
<openerp>
	<data>
		<record id="view_eiru_payments_invoices" model="ir.ui.view">
			<field name="name">view.eiru.payments.invoices</field>
			<field name="model">account.invoice</field>
			<field name="inherit_id" ref="account.invoice_form"/>
			<field name="arch" type="xml">
				<xpath expr="//button[@name='invoice_pay_customer']" position="replace">
					<div class="eiru-payments-invoices" attrs="{'invisible': [('state','!=','open')]}"> </div>
				</xpath>
			</field>
		</record>
		<record id="view_eiru_payments_invoices_supplier" model="ir.ui.view">
			<field name="name">view.eiru.payments.invoices.supplier</field>
			<field name="model">account.invoice</field>
			<field name="inherit_id" ref="account.invoice_supplier_form"/>
			<field name="arch" type="xml">
				<xpath expr="//button[@name='invoice_pay_customer']" position="replace">
					<div class="eiru-payments-invoices" attrs="{'invisible': [('state','!=','open')]}"> </div>
				</xpath>
			</field>
		</record>

		<record id="view_eiru_payments_invoices_voucher_customer" model="ir.ui.view">
			<field name="name">view.eiru.payments.invoices.voucher.customer</field>
			<field name="model">account.invoice</field>
			<field name="inherit_id" ref="account_voucher.view_invoice_customer"/>
			<field name="arch" type="xml">
				<xpath expr="//button[@name='invoice_pay_customer']" position="replace"></xpath>
			</field>
		</record>
	</data>
</openerp>