diff --git a/CHANGELOG.md b/CHANGELOG.md
index b1e0a4b..50e3b2a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+v 1.31.1 [28-ago-2019]
+----------------------
+    - Error: Al agregar nuevo impuesto #369
+
+
 v 1.31.0 [23-abr-2019]
 ----------------------
     - Error: Validar cantidad o valor unitario cero en tickets
diff --git a/README.md b/README.md
index 9935ff6..44f0eed 100644
--- a/README.md
+++ b/README.md
@@ -19,7 +19,7 @@ contratar: administracion ARROBA empresalibre.net
 
 * Servidor web, recomendado Nginx
 * uwsgi
-* python3
+* python3.6+
 * xsltproc
 * openssl
 * xmlsec
diff --git a/VERSION b/VERSION
index 34aae15..6bae540 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.31.0
+1.31.1
diff --git a/source/app/models/main.py b/source/app/models/main.py
index c90c18e..59fcd25 100644
--- a/source/app/models/main.py
+++ b/source/app/models/main.py
@@ -3663,6 +3663,8 @@ class Facturas(BaseModel):
 
     @classmethod
     def validate_count_partners(cls, ids):
+        """Validate if invoices IDs are of unique client"""
+
         filters = (Facturas.id.in_(tuple(ids.keys())))
         partners = (Facturas.select(fn.COUNT(Socios.rfc))
             .where(filters)
@@ -5275,6 +5277,16 @@ class Facturas(BaseModel):
 
         return {'ok': False}
 
+    # ~ v2
+    @classmethod
+    def uncancel(cls, id):
+        obj = Facturas.get(Facturas.id==id)
+        if obj.uuid is None:
+            msg = 'La factura no esta timbrada'
+            return {'ok': False, 'msg': msg}
+
+        return
+
 
 class PreFacturas(BaseModel):
     cliente = ForeignKeyField(Socios)
@@ -9974,6 +9986,8 @@ def _exportar_documentos():
     if not month:
         month = str(n.month)
 
+    without_stamp = []
+
     filters = {
         'year': year,
         'month': month,
@@ -9986,6 +10000,8 @@ def _exportar_documentos():
                 i+1, t, row['serie'], row['folio'])
             log.info(msg)
             _, name = Facturas.get_xml(row['id'])
+            if not row['uuid']:
+                without_stamp.append(f"{row['serie']}-{row['folio']}")
             msg = '\tXML extraido...'
             log.info(msg)
             name = name[:-3] + 'pdf'
@@ -9998,6 +10014,8 @@ def _exportar_documentos():
             log.info(msg)
 
     log.info('Documentos exportados...')
+    for i in without_stamp:
+        log.info(i)
     return
 
 
diff --git a/source/app/settings.py b/source/app/settings.py
index b5b809d..dbe8d15 100644
--- a/source/app/settings.py
+++ b/source/app/settings.py
@@ -47,7 +47,7 @@ except ImportError:
 
 
 DEBUG = DEBUG
-VERSION = '1.31.0'
+VERSION = '1.31.1'
 EMAIL_SUPPORT = ('soporte@empresalibre.mx',)
 TITLE_APP = '{} v{}'.format(TITLE_APP, VERSION)
 
diff --git a/source/static/js/controller/admin.js b/source/static/js/controller/admin.js
index cbc3392..650b713 100644
--- a/source/static/js/controller/admin.js
+++ b/source/static/js/controller/admin.js
@@ -1640,7 +1640,7 @@ function cmd_agregar_impuesto_click(){
         return
     }
 
-    if(impuesto='ISR' || tasa > 0){
+    if(impuesto=='ISR' && tasa > 0){
         msg = 'El impuesto ISR debe ser tipo Retención'
         msg_error(msg)
         return