diff --git a/sale.py b/sale.py
index 8184e4b..b617aef 100644
--- a/sale.py
+++ b/sale.py
@@ -2,6 +2,7 @@ from trytond.pool import Pool, PoolMeta
 from trytond.model import ModelView, fields
 from trytond.transaction import Transaction
 from trytond.modules.currency.fields import Monetary
+from trytond.pyson import Eval
 from decimal import Decimal
 
 import requests
@@ -23,6 +24,7 @@ class Sale(metaclass=PoolMeta):
                 "Total Tip", digits='currency', currency='currency'),
         'get_amount')
     total_tip_cache = fields.Numeric("Total Tip cache", digits="currency")
+    
 
     @classmethod
     def __setup__(cls):
@@ -340,7 +342,19 @@ class Line(metaclass=PoolMeta):
     pizza = fields.Integer("Pizza")
     impreso = fields.Boolean("Impreso")
     bought_pizza = fields.Boolean("Sold pizza")
+    rate = fields.Numeric(
+            "Rate", digits=(16, 4),
+            states={
+                'invisible': Eval('type') != 'line',
+                'readonly': Eval('sale_state') != 'draft',
+                },
+            depends=['type', 'sale_state'])
 
+
+    @classmethod
+    def default_rate(cls):
+        return 0
+    
     @fields.depends('product', 'unit', 'sale',
                     '_parent_sale.party', '_parent_sale.invoice_party',
                     '_parent_sale.pizza_number',
@@ -359,3 +373,8 @@ class Line(metaclass=PoolMeta):
         Production = super(Line, self).get_production()
 
         return Production
+
+    @fields.depends('discount_rate')
+    def on_change_discount_rate(self):
+        if self.discount_rate:
+            self.rate = self.discount_rate
diff --git a/view/sale_line_form.xml b/view/sale_line_form.xml
index 5a0105a..1d590ed 100644
--- a/view/sale_line_form.xml
+++ b/view/sale_line_form.xml
@@ -10,4 +10,8 @@
 	<label name="bought_pizza"/>
 	<field name="bought_pizza"/>
     </xpath>
+    <xpath expr="//field[@name='discount_rate']" position="after">
+	<label name="discount_rate"/>
+	<field name="discount_rate"  factor="100"/>
+    </xpath>
 </data>