diff --git a/golem_resource_account/models/golem_resource_reservation.py b/golem_resource_account/models/golem_resource_reservation.py
index cfa2b0d..e5209db 100644
--- a/golem_resource_account/models/golem_resource_reservation.py
+++ b/golem_resource_account/models/golem_resource_reservation.py
@@ -40,6 +40,9 @@ class GolemResourceReservation(models.Model):
     def create_invoice(self):
         """ Invoice creation """
         for reservation in self:
+            if reservation.invoice_line_id:
+                raise ValidationError(_('You can not create an invoice as there '
+                                        'is already one.'))
             inv_obj = self.env['account.invoice']
             partner_id = reservation.partner_id
             product = reservation.resource_id.product_tmpl_id
@@ -66,11 +69,11 @@ class GolemResourceReservation(models.Model):
                 'invoice_line_ids': [(0, 0, {
                     'name': reservation.resource_id.name,
                     'origin': reservation.name,
-                    'account_id': account_id,
                     'price_unit': amount,
                     'quantity': 1.0,
-                    'discount': 0.0,
                     'uom_id': product.uom_id.id,
+                    'account_id': account_id,
                     'product_id': product.id,
-                    })]
-                })
+                })]
+            })
+            reservation.invoice_line_id = reservation.invoice_id.invoice_line_ids[0]
diff --git a/golem_resource_account/views/golem_resource_reservation_views.xml b/golem_resource_account/views/golem_resource_reservation_views.xml
index 00590f1..f25975b 100644
--- a/golem_resource_account/views/golem_resource_reservation_views.xml
+++ b/golem_resource_account/views/golem_resource_reservation_views.xml
@@ -28,6 +28,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
       <field name='inherit_id' ref="golem_resource.golem_resource_reservation_view_tree"/>
       <field name="arch" type="xml">
         <field name="state" position="after">
+          <field name="invoice_id" />
           <field name="invoice_state" string="Invoice status" />
         </field>
       </field>
@@ -42,11 +43,10 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
       <field name="arch" type="xml">
         <button name="state_rejected"  position="after">
           <button name="create_invoice" type="object" string="Create Invoice" class="oe_highlight"
-            attrs="{'invisible': ['|', ('state', '!=', 'validated'), ('resource_product_id', '=', False)]}" />
+            attrs="{'invisible': ['|', ('state', '!=', 'validated'), '|', ('resource_product_id', '=', False), ('invoice_id', '!=', False)]}" />
         </button>
         <group name="reservation" position="after">
           <group name="invoicing" string="Invoicing"
-            attrs="{'invisible': ['|', ('state', '!=', 'validated'), ('resource_product_id', '=', False)]}">
             attrs="{'invisible': [('invoice_id', '=', False)]}">
             <field name="resource_product_id" />
             <field name="invoice_id" />