diff --git a/src/budy/models/order.py b/src/budy/models/order.py
index 8a73507..37e2946 100644
--- a/src/budy/models/order.py
+++ b/src/budy/models/order.py
@@ -975,6 +975,7 @@ def mark_paid_s(self):
     def unmark_paid_s(self):
         self.status = "waiting_payment"
         self.paid = False
+        self.increment_inventory_s()
         self.save()
 
     @appier.operation(name = "Mark Invoiced")
@@ -1084,6 +1085,22 @@ def decrement_inventory_s(self, force = False):
         self.inventory_decremented = True
         self.save()
 
+    @appier.operation(
+        name = "Increment Inventory",
+        description = """Increments the inventory stock levels
+        according to order lines (reverses the decrement stock
+        operation, restoring the stock back)""",
+        parameters = (("Force", "force", bool, False),),
+        level = 2
+    )
+    def increment_inventory_s(self, force = False):
+        if not self.inventory_decremented and not force: return
+        for line in self.lines:
+            line.merchandise.quantity_hand += line.quantity
+            line.merchandise.save()
+        self.inventory_decremented = False
+        self.save()
+
     @appier.operation(
         name = "Import Omni",
         parameters = (
diff --git a/src/budy/test/order.py b/src/budy/test/order.py
index 0dee17d..be8066b 100644
--- a/src/budy/test/order.py
+++ b/src/budy/test/order.py
@@ -60,7 +60,8 @@ def test_basic(self):
         product = budy.Product(
             short_description = "product",
             gender = "Male",
-            price = 10.0
+            price = 10.0,
+            quantity_hand = 5.0
         )
         product.save()
 
@@ -79,6 +80,7 @@ def test_basic(self):
         self.assertEqual(order.currency, None)
         self.assertEqual(order.total >= 0.0, True)
         self.assertEqual(order.paid, False)
+        self.assertEqual(order.inventory_decremented, False)
         self.assertEqual(order.date, None)
         self.assertEqual(order.notifications, [])
 
@@ -137,11 +139,17 @@ def test_basic(self):
 
         self.assertEqual(order.status, "waiting_payment")
         self.assertEqual(order.paid, False)
+        self.assertEqual(order.inventory_decremented, False)
 
         order.mark_paid_s()
 
         self.assertEqual(order.status, "paid")
         self.assertEqual(order.paid, True)
+        self.assertEqual(order.inventory_decremented, True)
+
+        product = product.reload()
+
+        self.assertEqual(product.quantity_hand, 3)
 
         self.assertRaises(appier.AssertionError, order.mark_paid_s)
 
@@ -390,6 +398,7 @@ def _pay_dummy(payment_data):
         self.assertEqual(order.is_valid(), True)
         self.assertEqual(order_line.is_valid_quantity(), True)
         self.assertEqual(order.paid, False)
+        self.assertEqual(order.inventory_decremented, False)
         self.assertEqual(order.status, "waiting_payment")
 
         self.assertRaises(
@@ -404,7 +413,8 @@ def test_voucher_use(self):
         product = budy.Product(
             short_description = "product",
             gender = "Male",
-            price = 10.0
+            price = 10.0,
+            quantity_hand = 5.0
         )
         product.save()
 
@@ -453,6 +463,7 @@ def test_voucher_use(self):
         self.assertEqual(order.is_valid(), True)
         self.assertEqual(order_line.is_valid_quantity(), True)
         self.assertEqual(order.paid, False)
+        self.assertEqual(order.inventory_decremented, False)
         self.assertEqual(order.status, "waiting_payment")
 
         order.end_pay_s(
@@ -470,6 +481,11 @@ def test_voucher_use(self):
         self.assertEqual(order_line.is_valid_quantity(), True)
         self.assertEqual(order.paid, True)
         self.assertEqual(order.status, "paid")
+        self.assertEqual(order.inventory_decremented, True)
+
+        product = product.reload()
+
+        self.assertEqual(product.quantity_hand, 3.0)
 
         order.date = None
         order.status = "created"
@@ -494,6 +510,7 @@ def test_voucher_use(self):
         self.assertEqual(order.is_valid(), True)
         self.assertEqual(order_line.is_valid_quantity(), True)
         self.assertEqual(order.paid, False)
+        self.assertEqual(order.inventory_decremented, False)
         self.assertEqual(order.status, "waiting_payment")
 
         order.cancel_s()
@@ -509,6 +526,7 @@ def test_voucher_use(self):
         self.assertEqual(order.is_valid(), True)
         self.assertEqual(order_line.is_valid_quantity(), True)
         self.assertEqual(order.paid, False)
+        self.assertEqual(order.inventory_decremented, False)
         self.assertEqual(order.status, "canceled")
 
         order.date = None
@@ -539,8 +557,13 @@ def test_voucher_use(self):
         self.assertEqual(order.is_valid(), True)
         self.assertEqual(order_line.is_valid_quantity(), True)
         self.assertEqual(order.paid, True)
+        self.assertEqual(order.inventory_decremented, True)
         self.assertEqual(order.status, "paid")
 
+        product = product.reload()
+
+        self.assertEqual(product.quantity_hand, 3.0)
+
         order.cancel_s()
 
         voucher = voucher.reload()
@@ -554,6 +577,7 @@ def test_voucher_use(self):
         self.assertEqual(order.is_valid(), True)
         self.assertEqual(order_line.is_valid_quantity(), True)
         self.assertEqual(order.paid, True)
+        self.assertEqual(order.inventory_decremented, True)
         self.assertEqual(order.status, "canceled")
 
     def test_discount(self):
@@ -931,7 +955,8 @@ def test_free(self):
         product = budy.Product(
             short_description = "product",
             gender = "Male",
-            price = 10.0
+            price = 10.0,
+            quantity_hand = 5.0
         )
         product.save()
 
@@ -972,6 +997,7 @@ def test_free(self):
         self.assertEqual(order.payable, 0.0)
         self.assertEqual(order.discountable, 20.0)
         self.assertEqual(order.paid, False)
+        self.assertEqual(order.inventory_decremented, False)
         self.assertEqual(isinstance(order.sub_total, commons.Decimal), True)
         self.assertEqual(isinstance(order.discount, commons.Decimal), True)
         self.assertEqual(isinstance(order.total, commons.Decimal), True)
@@ -986,6 +1012,7 @@ def test_free(self):
         self.assertEqual(order.payable, 0.0)
         self.assertEqual(order.discountable, 20.0)
         self.assertEqual(order.paid, True)
+        self.assertEqual(order.inventory_decremented, True)
         self.assertEqual(order.payment_data, {})
         self.assertEqual(isinstance(order.sub_total, commons.Decimal), True)
         self.assertEqual(isinstance(order.discount, commons.Decimal), True)
@@ -993,6 +1020,10 @@ def test_free(self):
         self.assertEqual(isinstance(order.payable, commons.Decimal), True)
         self.assertEqual(isinstance(order.discountable, commons.Decimal), True)
 
+        product = product.reload()
+
+        self.assertEqual(product.quantity_hand, 3.0)
+
     def test_closed(self):
         order = budy.Order()
         order.save()
@@ -1034,7 +1065,8 @@ def test_payment_method(self):
         product = budy.Product(
             short_description = "product",
             gender = "Male",
-            price = 10.0
+            price = 10.0,
+            quantity_hand = 5.0
         )
         product.save()
 
@@ -1067,6 +1099,7 @@ def test_payment_method(self):
         self.assertEqual(order.is_valid(), True)
         self.assertEqual(order_line.is_valid_quantity(), True)
         self.assertEqual(order.paid, False)
+        self.assertEqual(order.inventory_decremented, False)
         self.assertEqual(order.status, "created")
 
         self.assertRaises(
@@ -1082,6 +1115,7 @@ def test_payment_method(self):
         self.assertEqual(order.is_valid(), True)
         self.assertEqual(order_line.is_valid_quantity(), True)
         self.assertEqual(order.paid, False)
+        self.assertEqual(order.inventory_decremented, False)
         self.assertEqual(order.status, "waiting_payment")
 
         self.assertRaises(
@@ -1099,8 +1133,13 @@ def test_payment_method(self):
         self.assertEqual(order.is_valid(), True)
         self.assertEqual(order_line.is_valid_quantity(), True)
         self.assertEqual(order.paid, True)
+        self.assertEqual(order.inventory_decremented, True)
         self.assertEqual(order.status, "paid")
 
+        product = product.reload()
+
+        self.assertEqual(product.quantity_hand, 3.0)
+
     def test__build_notes(self):
         product = budy.Product(
             short_description = "product",