diff --git a/partner_event/__manifest__.py b/partner_event/__manifest__.py
index ad6377189..312807ddb 100644
--- a/partner_event/__manifest__.py
+++ b/partner_event/__manifest__.py
@@ -5,11 +5,12 @@
 # Copyright 2017 Tecnativa S.L. - David Vidal
 # Copyright 2018 Jupical Technologies Pvt. Ltd. - Anil Kesariya
 # Copyright 2020 Tecnativa S.L. - Víctor Martínez
+# Copyright 2023 Tecnativa S.L. - Carolina Fernandez
 # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
 
 {
     "name": "Link partner to events",
-    "version": "15.0.1.0.0",
+    "version": "16.0.1.0.0",
     "category": "Marketing",
     "author": "Tecnativa," "Odoo Community Association (OCA)",
     "website": "https://github.com/OCA/event",
diff --git a/partner_event/models/event_registration.py b/partner_event/models/event_registration.py
index c830e2997..9cfb81d94 100644
--- a/partner_event/models/event_registration.py
+++ b/partner_event/models/event_registration.py
@@ -1,10 +1,11 @@
-# Copyright 2014 Tecnativa S.L. - Pedro M. Baeza
-# Copyright 2015 Tecnativa S.L. - Javier Iniesta
-# Copyright 2016 Tecnativa S.L. - Antonio Espinosa
-# Copyright 2016 Tecnativa S.L. - Vicent Cubells
-# Copyright 2020 Tecnativa S.L. - Víctor Martínez
+# Copyright 2015 Tecnativa - Javier Iniesta
+# Copyright 2016 Tecnativa - Antonio Espinosa
+# Copyright 2016 Tecnativa - Vicent Cubells
+# Copyright 2018 Jupical Technologies Pvt. Ltd. - Anil Kesariya
+# Copyright 2020 Tecnativa - Víctor Martínez
+# Copyright 2014-2023 Tecnativa - Pedro M. Baeza
+# Copyright 2023 Tecnativa - Carolina Fernandez
 # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
-
 from odoo import api, fields, models
 
 
@@ -17,6 +18,7 @@ class EventRegistration(models.Model):
         string="Attendee Partner",
         ondelete="restrict",
         copy=False,
+        index=True,
     )
 
     def _prepare_partner(self, vals):
@@ -64,7 +66,12 @@ def _onchange_partner_id(self):
             get_attendee_partner_address = {
                 "get_attendee_partner_address": self.attendee_partner_id,
             }
-            return super(
-                EventRegistration, self.with_context(**get_attendee_partner_address)
-            )._onchange_partner_id()
-        return super(EventRegistration, self)._onchange_partner_id()
+            self = self.with_context(**get_attendee_partner_address)
+            for registration in self:
+                if registration.partner_id:
+                    registration.update(
+                        registration._synchronize_partner_values(
+                            registration.partner_id
+                        )
+                    )
+        return {}
diff --git a/partner_event/readme/CONTRIBUTORS.rst b/partner_event/readme/CONTRIBUTORS.rst
index 736ece26e..91f0d5fc7 100644
--- a/partner_event/readme/CONTRIBUTORS.rst
+++ b/partner_event/readme/CONTRIBUTORS.rst
@@ -8,6 +8,7 @@
   * Rafael Blasco
   * Víctor Martínez
   * Stefan Ungureanu
+  * Carolina Fernandez
 
 * `Antiun <https://antiun.com/>`__:
 
diff --git a/partner_event/readme/DESCRIPTION.rst b/partner_event/readme/DESCRIPTION.rst
index 9c2e259c5..2360047bb 100644
--- a/partner_event/readme/DESCRIPTION.rst
+++ b/partner_event/readme/DESCRIPTION.rst
@@ -10,3 +10,4 @@ It also includes:
 * Action in partner tree view 'More' button, to register several partners
   to an event
 * Restricts partner deletion when event attendees are linked to it.
+* Onchange for partner_id removed in v16 core in Event Registration- including functionality here
diff --git a/partner_event/static/description/index.html b/partner_event/static/description/index.html
index 4ad43f5db..ecad89690 100644
--- a/partner_event/static/description/index.html
+++ b/partner_event/static/description/index.html
@@ -431,6 +431,7 @@ <h2><a class="toc-backref" href="#id5">Contributors</a></h2>
 <li>Rafael Blasco</li>
 <li>Víctor Martínez</li>
 <li>Stefan Ungureanu</li>
+<li>Carolina Fernandez/li>
 </ul>
 </li>
 <li><a class="reference external" href="https://antiun.com/">Antiun</a>:<ul>
diff --git a/partner_event/tests/test_event_registration.py b/partner_event/tests/test_event_registration.py
index 0eccd6f4d..0b65b07f8 100644
--- a/partner_event/tests/test_event_registration.py
+++ b/partner_event/tests/test_event_registration.py
@@ -63,12 +63,12 @@ def test_count_registrations(self):
         event_1 = self.event_0.copy()
         self.assertEqual(self.partner_01.registration_count, 0)
         self.registration_01.state = "open"
-        self.partner_01.invalidate_cache()
+        self.partner_01.invalidate_recordset()
         self.assertEqual(self.partner_01.registration_count, 1)
         self.registration_02.state = "done"
         self.registration_02.attendee_partner_id = self.partner_01
         self.registration_02.event_id = event_1
-        self.partner_01.invalidate_cache()
+        self.partner_01.invalidate_recordset()
         self.assertEqual(self.partner_01.registration_count, 2)
 
     def test_button_register(self):
@@ -81,16 +81,16 @@ def test_data_update(self):
         event_2 = self.event_0.copy()
         self.yesterday = datetime.now() - timedelta(days=1)
         self.tomorrow = datetime.now() + timedelta(days=1)
-        self.last_moth = datetime.now() - timedelta(days=30)
+        self.last_month = datetime.now() - timedelta(days=30)
         # Set an old event
-        event_2.write({"date_begin": self.last_moth})
+        event_2.write({"date_begin": self.last_month})
         event_2.write({"date_end": self.yesterday})
         self.registration_02.event_id = event_2
         self.registration_02.attendee_partner_id = self.partner_01
         # Update partner for an old event
         self.partner_01.write({"email": "new@test.com"})
         self.assertNotEqual(event_2.registration_ids.email, "new@test.com")
-        # Update partner for an current event
+        # Update partner for a current event
         event_2.write({"date_end": self.tomorrow})
         self.partner_01.write({"email": "new@test.com"})
         self.assertEqual(event_2.registration_ids.email, "new@test.com")
diff --git a/partner_event/wizard/res_partner_register_event.py b/partner_event/wizard/res_partner_register_event.py
index eb5c6bb8d..951513f23 100644
--- a/partner_event/wizard/res_partner_register_event.py
+++ b/partner_event/wizard/res_partner_register_event.py
@@ -1,9 +1,9 @@
-# Copyright 2014 Tecnativa S.L. - Pedro M. Baeza
-# Copyright 2015 Tecnativa S.L. - Javier Iniesta
-# Copyright 2016 Tecnativa S.L. - Antonio Espinosa
-# Copyright 2016 Tecnativa S.L. - Vicent Cubells
+# Copyright 2015 Tecnativa - Javier Iniesta
+# Copyright 2016 Tecnativa - Antonio Espinosa
+# Copyright 2016 Tecnativa - Vicent Cubells
 # Copyright 2018 Jupical Technologies Pvt. Ltd. - Anil Kesariya
-# Copyright 2020 Tecnativa S.L. - Víctor Martínez
+# Copyright 2020 Tecnativa - Víctor Martínez
+# Copyright 2014-2023 Tecnativa - Pedro M. Baeza
 # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html).
 
 from odoo import fields, models
@@ -11,13 +11,11 @@
 
 class ResPartnerRegisterEvent(models.TransientModel):
     _name = "res.partner.register.event"
-
     _description = "Register partner for event"
 
     event = fields.Many2one(
         comodel_name="event.event", required=True, ondelete="cascade"
     )
-    errors = fields.Text(readonly=True)
 
     def _prepare_registration(self, partner):
         return {
@@ -27,28 +25,19 @@ def _prepare_registration(self, partner):
             "name": partner.name,
             "email": partner.email,
             "phone": partner.phone,
-            "date_open": fields.Datetime.now(),
         }
 
     def button_register(self):
-        registration_obj = self.env["event.registration"]
-        errors = []
+        vals_list = []
+        Registration = self.env["event.registration"]
         for partner in self.env["res.partner"].browse(
             self.env.context.get("active_ids", [])
         ):
-            try:
-                with self.env.cr.savepoint():
-                    registration_obj.create(self._prepare_registration(partner))
-            except Exception:
-                errors.append(partner.name)
-        if errors:
-            self.errors = "\n".join(errors)
-            data_obj = self.env.ref("partner_event." "res_partner_register_event_view")
-            return {
-                "type": "ir.actions.act_window",
-                "res_model": self._name,
-                "view_mode": "form",
-                "view_id": [data_obj.id],
-                "res_id": self.id,
-                "target": "new",
-            }
+            if not Registration.search(
+                [
+                    ("event_id", "=", self.event.id),
+                    ("attendee_partner_id", "=", partner.id),
+                ]
+            ):
+                vals_list.append(self._prepare_registration(partner))
+        self.env["event.registration"].create(vals_list)
diff --git a/partner_event/wizard/res_partner_register_event_view.xml b/partner_event/wizard/res_partner_register_event_view.xml
index d3a54c514..c1846c61f 100644
--- a/partner_event/wizard/res_partner_register_event_view.xml
+++ b/partner_event/wizard/res_partner_register_event_view.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8" ?>
-<!-- Copyright 2016 Tecnativa S.L. - Vicent Cubells
+<!-- Copyright 2016 Tecnativa - Vicent Cubells
+     Copyright 2023 Tecnativa - Pedro M. Baeza
      Copyright 2018 Jupical Technologies Pvt. Ltd. - Anil kesariya
      License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html). -->
 <odoo>
@@ -8,22 +9,14 @@
         <field name="model">res.partner.register.event</field>
         <field name="arch" type="xml">
             <form string="Select event to register">
-                <group attrs="{'invisible': [('errors', '!=', False)]}">
+                <group>
                     <field
                         name="event"
                         options="{'no_create': True, 'no_create_edit':True}"
                     />
                 </group>
-                <group attrs="{'invisible': [('errors', '=', False)]}">
-                    <separator
-                        colspan="4"
-                        string="These partners haven't been registered because they\'re already
-                       registered or other error occurred"
-                    />
-                    <field nolabel="1" name="errors" colspan="4" />
-                </group>
                 <footer>
-                    <div attrs="{'invisible': [('errors', '!=', False)]}">
+                    <div>
                         <button
                             name="button_register"
                             type="object"