diff --git a/facho/fe/model/__init__.py b/facho/fe/model/__init__.py
index f144d32..74aaf01 100644
--- a/facho/fe/model/__init__.py
+++ b/facho/fe/model/__init__.py
@@ -2,6 +2,9 @@ import facho.model as model
 import facho.model.fields as fields
 from datetime import date, datetime
 
+class Name(model.Model):
+    __name__ = 'Name'
+
 class Date(model.Model):
     __name__ = 'Date'
 
@@ -51,23 +54,60 @@ class InvoicedQuantity(model.Model):
     code = fields.Attribute('unitCode', default='NAR')
 
 
-class PriceAmount(model.Model):
-    __name__ = 'PriceAmount'
+class Amount(model.Model):
+    __name__ = 'Amount'
 
     currency = fields.Attribute('currencyID', default='COP')
     
 class Price(model.Model):
     __name__ = 'Price'
 
-    amount = fields.Many2One(PriceAmount)
+    amount = fields.Many2One(Amount, name='PriceAmount')
 
     def __default_set__(self, value):
         self.amount = value
 
+class Percent(model.Model):
+    __name__ = 'Percent'
+
+class TaxScheme(model.Model):
+    __name__ = 'TaxScheme'
+
+    id = fields.Many2One(ID)
+    name= fields.Many2One(Name)
+
+class TaxCategory(model.Model):
+    __name__ = 'TaxCategory'
+
+    percent = fields.Many2One(Percent, default='19.0')
+    tax_scheme = fields.Many2One(TaxScheme)
+    
+class TaxSubTotal(model.Model):
+    __name__ = 'TaxSubTotal'
+
+    taxable_amount = fields.Many2One(Amount, name='TaxableAmount')
+    tax_amount = fields.Many2One(Amount, name='TaxAmount')
+    tax_category = fields.Many2One(TaxCategory)
+
+    percent = fields.Virtual(setter='set_percent')
+
+    def set_percent(self, name, value):
+        self.tax_category.percent = value
+        # TODO(bit4bit) hacer variable
+        self.tax_category.tax_scheme.id = '01'
+        self.tax_category.tax_scheme.name = 'IVA'
+    
+class TaxTotal(model.Model):
+    __name__ = 'TaxTotal'
+
+    tax_amount = fields.Many2One(Amount, name='TaxAmount')
+    subtotals = fields.One2Many(TaxSubTotal)
+    
 class InvoiceLine(model.Model):
     __name__ = 'InvoiceLine'
 
     quantity = fields.Many2One(InvoicedQuantity)
+    taxtotal = fields.Many2One(TaxTotal)
     price = fields.Many2One(Price)
     
 class Invoice(model.Model):
diff --git a/facho/model/__init__.py b/facho/model/__init__.py
index 9a45981..e70b903 100644
--- a/facho/model/__init__.py
+++ b/facho/model/__init__.py
@@ -38,10 +38,11 @@ class ModelBase(object, metaclass=ModelMeta):
         # forzamos registros de campos al modelo
         # al instanciar
         for (key, v) in type(obj).__dict__.items():
+                
             if isinstance(v, fields.Attribute) or isinstance(v, fields.Many2One) or isinstance(v, fields.Function):
                 if hasattr(v, 'default') and v.default is not None:
                     setattr(obj, key, v.default)
-
+                
                 # register callbacks for changes
                 (fun, on_change_fields) = on_change_fields_for_function()
                 for field in on_change_fields:
@@ -97,7 +98,7 @@ class ModelBase(object, metaclass=ModelMeta):
 
         content = ""
 
-        for name, value in self._fields.items():
+        for value in self._fields.values():
             if hasattr(value, 'to_xml'):
                 content += value.to_xml()
             elif isinstance(value, str):
diff --git a/facho/model/fields/one2many.py b/facho/model/fields/one2many.py
index 182a1b0..112a92f 100644
--- a/facho/model/fields/one2many.py
+++ b/facho/model/fields/one2many.py
@@ -19,7 +19,6 @@ class _RelationProxy():
         # algo burdo, se usa __dict__ para saltarnos el __getattr__ y generar un fallo por recursion
         for fun in self.__dict__['_inst']._on_change_fields[self.__dict__['_attribute']]:
             fun(self.__dict__['_inst'], self.__dict__['_attribute'], value)
-
         return setattr(self._obj, attr, value)
 
 class _Relation():
diff --git a/tests/test_model_invoice.py b/tests/test_model_invoice.py
index d85c87b..6e6b49e 100644
--- a/tests/test_model_invoice.py
+++ b/tests/test_model_invoice.py
@@ -21,6 +21,10 @@ def test_simple_invoice():
 
     line = invoice.lines.create()
     line.quantity = form.Quantity(1, '94')
+    subtotal = line.taxtotal.subtotals.create()
+    subtotal.percent = 19.0
+    # TODO(bit4bit) el orden de los elementos
+    # en el xml lo debe determinar la declaracion en los modelos
     line.price = form.Amount(5_000)
 
-    assert '<Invoice><ID>323200000129</ID><IssueDate>2019-01-16T10:53:10-05:00</IssueDate><IssueTime>10:5310-05:00</IssueTime><AccountingSupplierParty><Party><ID>700085371</ID></Party></AccountingSupplierParty><AccountingCustomerParty><Party><ID>800199436</ID></Party></AccountingCustomerParty><InvoiceLine><InvoiceQuantity unitCode="NAR">1.0</InvoiceQuantity><Price><PriceAmount currencyID="COP">5000.0</PriceAmount></Price></InvoiceLine></Invoice>' == invoice.to_xml()
+    assert '<Invoice><ID>323200000129</ID><IssueDate>2019-01-16T10:53:10-05:00</IssueDate><IssueTime>10:5310-05:00</IssueTime><AccountingSupplierParty><Party><ID>700085371</ID></Party></AccountingSupplierParty><AccountingCustomerParty><Party><ID>800199436</ID></Party></AccountingCustomerParty><InvoiceLine><InvoiceQuantity unitCode="NAR">1.0</InvoiceQuantity><TaxTotal><TaxSubTotal><TaxCategory><Percent>19.0</Percent><TaxScheme><ID>01</ID><Name>IVA</Name></TaxScheme></TaxCategory></TaxSubTotal></TaxTotal><Price><PriceAmount currencyID="COP">5000.0</PriceAmount></Price></InvoiceLine></Invoice>' == invoice.to_xml()