diff --git a/models/account_invoice.py b/models/account_invoice.py
index be64873..5619c0a 100755
--- a/models/account_invoice.py
+++ b/models/account_invoice.py
@@ -4,16 +4,26 @@ from ..utils import MODULE_NAME
 
 
 class AccountInvoice(models.Model):
-    _inherit = "account.invoice"
+    _inherit = "account.move"
 
-    def invoice_print(self):
-        self.ensure_one()
+    @staticmethod
+    def check_contract_presence(sale_order_ids):
+        error_message = ""
+        if any(not so.contract_annex_id.contract_id for so in sale_order_ids):
+            error_message = _("There is a Sale order without binding contract.")
+        if any(not so.contract_annex_id  for so in sale_order_ids):
+            error_message = _("There is a Sale order without annex.")
+        if error_message:
+            raise UserError(error_message)
+
+    def action_invoice_print(self):
+        '''
         for so in self.env["sale.order"].search([]):
             if self.id in so.invoice_ids.ids:
                 order = so
                 break
         else:
-            return super().invoice_print()
+            return super().action_invoice_print()
 
         if not order.contract_annex_id or not order.contract_annex_id.contract_id:
             raise UserError(
@@ -21,8 +31,20 @@ class AccountInvoice(models.Model):
                     "There is no binding contract. It is necessary to link the order with the annex to the contract."
                 )
             )
-
         self.sent = True
+        '''
+
+        sale_orders_ids = self.env["sale.order"].search([
+            ("invoice_ids", "in", self.ids)
+        ])
+        if not sale_orders_ids:
+            return super().action_invoice_print()
+
+        self.check_contract_presence(sale_orders_ids)
+        self.filtered(lambda inv: not inv.is_move_sent).write({'is_move_sent': True})
+
+
+
 
         view = self.env.ref(
             "{}.res_partner_wizard_print_document_view".format(MODULE_NAME)