diff --git a/README.md b/README.md
index e17d4ed..cf2ac1e 100644
--- a/README.md
+++ b/README.md
@@ -12,10 +12,22 @@ $ pip install git+https://git.disroot.org/Etrivial/facho
 
 al instalar el paquete se genera el comando *facho*
 
-## COMMANDO: generate-invoice
-
-genera factura xml desde archiv .py ver *examples/generate-invoice-invoice.py*.
 
 ## COMENTARIOS
 
   * http://facturasyrespuestas.com/2342/error-al-enviar-set-de-pruebas-usando-sendtestsetasync
+
+# CÓMO CONTRIBUIR?
+
+## INSTALAR USANDO python develop
+
+este enlaza el ejecutable **facho** en lugar de copiarlo.
+
+## CUMPLIR ANEXO TECNICO
+
+el archivo **docs/DIAN/Anexo_Tecnico_Factura_Electronica_Vr1_7_2020.pdf** describe la implementación de la
+facturación, la libreria **facho.py** permite crear elementos xml usando XPath-Like con el proposito
+de facilitar la relación entre el anexo y la implementación.
+
+  * facho/form.py: generación de Invoice XML.
+  * facho/fe.py: extensiones XML, ejemplo CUFE, Firma, etc..
\ No newline at end of file
diff --git a/facho/fe/fe.py b/facho/fe/fe.py
index dfcd786..4619122 100644
--- a/facho/fe/fe.py
+++ b/facho/fe/fe.py
@@ -225,9 +225,6 @@ class DianXMLExtensionSigner(FachoXMLExtension):
         ki = xmlsig.template.ensure_key_info(signature, name=id_keyinfo)
         data = xmlsig.template.add_x509_data(ki)
         xmlsig.template.x509_data_add_certificate(data)
-        serial = xmlsig.template.x509_data_add_issuer_serial(data)
-        xmlsig.template.x509_issuer_serial_add_issuer_name(serial)
-        xmlsig.template.x509_issuer_serial_add_serial_number(serial)
 
 
         xmlsig.template.add_key_value(ki)
diff --git a/facho/fe/form.py b/facho/fe/form.py
index d0a107c..77f2761 100644
--- a/facho/fe/form.py
+++ b/facho/fe/form.py
@@ -485,6 +485,10 @@ class DIANInvoiceXML(fe.FeXML):
                           invoice.invoice_customer.address.country.code)
 
         fexml.placeholder_for('/fe:Invoice/cac:AccountingCustomerParty/cac:Party/cac:PartyTaxScheme/cac:TaxScheme')
+        fexml.set_element('/fe:Invoice/cac:AccountingCustomerParty/cac:Party/cac:PartyTaxScheme/cac:TaxScheme/cbc:ID',
+                          'Zy')
+        fexml.set_element('/fe:Invoice/cac:AccountingCustomerParty/cac:Party/cac:PartyTaxScheme/cac:TaxScheme/cbc:Name',
+                          'No causa')
 
         fexml.placeholder_for('/fe:Invoice/cac:AccountingCustomerParty/cac:Party/cac:PartyLegalEntity')
         fexml.set_element('/fe:Invoice/cac:AccountingCustomerParty/cac:Party/cac:PartyLegalEntity/cbc:RegistrationName',
@@ -496,6 +500,9 @@ class DIANInvoiceXML(fe.FeXML):
 
         fexml.set_element('/fe:Invoice/cac:AccountingCustomerParty/cac:Party/cac:PartyLegalEntity/cac:RegistrationAddress/cac:Country/cbc:IdentificationCode', invoice.invoice_customer.address.country.code)
         fexml.set_element('/fe:Invoice/cac:AccountingCustomerParty/cac:Party/cac:PartyLegalEntity/cac:RegistrationAddress/cac:Country/cbc:Name', invoice.invoice_customer.address.country.name)
+        #DIAN 1.7.-2020: FAK55
+        fexml.set_element('/fe:Invoice/cac:AccountingCustomerParty/cac:Party/cac:Contact/cbc:ElectronicMail',
+                          invoice.invoice_customer.email)
 
     def set_payment_mean(fexml, invoice):
         payment_mean = invoice.invoice_payment_mean
@@ -533,10 +540,11 @@ class DIANInvoiceXML(fe.FeXML):
         #requeridos para CUFE
         tax_amount_for['01']['tax_amount'] = 0.0
         tax_amount_for['01']['taxable_amount'] = 0.0
-        tax_amount_for['04']['tax_amount'] = 0.0
-        tax_amount_for['04']['taxable_amount'] = 0.0
-        tax_amount_for['03']['tax_amount'] = 0.0
-        tax_amount_for['03']['taxable_amount'] = 0.0
+        #DIAN 1.7.-2020: FAS07 => Se debe construir estrategia para  su manejo
+        #tax_amount_for['04']['tax_amount'] = 0.0
+        #tax_amount_for['04']['taxable_amount'] = 0.0
+        #tax_amount_for['03']['tax_amount'] = 0.0
+        #tax_amount_for['03']['taxable_amount'] = 0.0
 
         total_tax_amount = 0.0
 
@@ -613,7 +621,9 @@ class DIANInvoiceXML(fe.FeXML):
             line.set_element('/cac:InvoiceLine/cac:Item/cbc:Description', invoice_line.item.description)
             # TODO
             line.set_element('/cac:InvoiceLine/cac:Item/cac:StandardItemIdentification/cbc:ID', invoice_line.item.id) 
-            line.set_element('/cac:InvoiceLine/cac:Price/cbc:PriceAmount', invoice_line.price.amount, currencyID="COP") 
+            line.set_element('/cac:InvoiceLine/cac:Price/cbc:PriceAmount', invoice_line.price.amount, currencyID="COP")
+            #DIAN 1.7.-2020: FBB04
+            line.set_element('/cac:InvoiceLine/cac:Price/cbc:BaseQuantity', invoice_line.price.amount) 
 
     def attach_invoice(fexml, invoice):
         """adiciona etiquetas a FEXML y retorna FEXML
diff --git a/requirements_dev.txt b/requirements_dev.txt
index 4ea07ea..f17ffa4 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -7,6 +7,7 @@ tox==3.5.2
 coverage==4.5.1
 Sphinx==1.8.1
 twine==1.12.1
+xmlsec==1.3.8
 
 pytest==3.8.2
 pytest-runner==4.2