eiru_inmobiliaria/models/account_invoice.py

# -*- coding: utf-8 -*-
from openerp import models, fields, api,_
from openerp.exceptions import Warning

class AnalyticAccount(models.Model):
    _inherit = 'account.invoice'

    # cuotas
    cuotas = fields.Char(string="Cuotas")
    cuota_total = fields.Integer(string="Total de cuotas")