diff --git a/apps/activity/forms.py b/apps/activity/forms.py
index 533ff7d1..4a13c230 100644
--- a/apps/activity/forms.py
+++ b/apps/activity/forms.py
@@ -1,6 +1,6 @@
 # Copyright (C) 2018-2020 by BDE ENS Paris-Saclay
 # SPDX-License-Identifier: GPL-3.0-or-later
-from datetime import timedelta
+from datetime import timedelta, datetime
 
 from django import forms
 from django.contrib.contenttypes.models import ContentType
@@ -41,6 +41,9 @@ class GuestForm(forms.ModelForm):
     def clean(self):
         cleaned_data = super().clean()
 
+        if self.activity.date_start > datetime.now():
+            self.add_error("inviter", _("You can't invite someone once the activity is started."))
+
         one_year = timedelta(days=365)
 
         qs = Guest.objects.filter(
diff --git a/apps/activity/models.py b/apps/activity/models.py
index feae60d7..b17a9f6e 100644
--- a/apps/activity/models.py
+++ b/apps/activity/models.py
@@ -1,6 +1,6 @@
 # Copyright (C) 2018-2020 by BDE ENS Paris-Saclay
 # SPDX-License-Identifier: GPL-3.0-or-later
-from datetime import timedelta
+from datetime import timedelta, datetime
 
 from django.contrib.auth.models import User
 from django.db import models
@@ -212,21 +212,25 @@ class Guest(models.Model):
     def save(self, force_insert=False, force_update=False, using=None, update_fields=None):
         one_year = timedelta(days=365)
 
-        qs = Guest.objects.filter(
-            first_name=self.first_name,
-            last_name=self.last_name,
-            activity__date_start__gte=self.activity.date_start - one_year,
-        )
-        if len(qs) >= 5:
-            raise ValidationError(_("This person has been already invited 5 times this year."))
+        if not force_insert:
+            if self.activity.date_start > datetime.now():
+                raise ValidationError(_("You can't invite someone once the activity is started."))
 
-        qs = qs.filter(activity=self.activity)
-        if qs.exists():
-            raise ValidationError(_("This person is already invited."))
+            qs = Guest.objects.filter(
+                first_name=self.first_name,
+                last_name=self.last_name,
+                activity__date_start__gte=self.activity.date_start - one_year,
+            )
+            if len(qs) >= 5:
+                raise ValidationError(_("This person has been already invited 5 times this year."))
 
-        qs = Guest.objects.filter(inviter=self.inviter, activity=self.activity)
-        if len(qs) >= 3:
-            raise ValidationError(_("You can't invite more than 3 people to this activity."))
+            qs = qs.filter(activity=self.activity)
+            if qs.exists():
+                raise ValidationError(_("This person is already invited."))
+
+            qs = Guest.objects.filter(inviter=self.inviter, activity=self.activity)
+            if len(qs) >= 3:
+                raise ValidationError(_("You can't invite more than 3 people to this activity."))
 
         return super().save(force_insert, force_update, using, update_fields)
 
diff --git a/apps/activity/views.py b/apps/activity/views.py
index 5df3493c..feb7591d 100644
--- a/apps/activity/views.py
+++ b/apps/activity/views.py
@@ -1,6 +1,6 @@
 # Copyright (C) 2018-2020 by BDE ENS Paris-Saclay
 # SPDX-License-Identifier: GPL-3.0-or-later
-from datetime import datetime
+from datetime import datetime, timezone
 
 from django.contrib.auth.mixins import LoginRequiredMixin
 from django.contrib.contenttypes.models import ContentType
@@ -61,6 +61,8 @@ class ActivityDetailView(LoginRequiredMixin, DetailView):
                            .filter(PermissionBackend.filter_queryset(self.request.user, Guest, "view")))
         ctx["guests"] = table
 
+        ctx["activity_started"] = datetime.now(timezone.utc) > self.object.date_start
+
         return ctx
 
 
diff --git a/apps/note/models/notes.py b/apps/note/models/notes.py
index d74d9147..89e2b31a 100644
--- a/apps/note/models/notes.py
+++ b/apps/note/models/notes.py
@@ -176,35 +176,6 @@ class NoteSpecial(Note):
         return self.special_type
 
 
-class NoteCommon(Note):
-    """
-    A :model:`note.Note` for special accounts, where real money enter or leave the system
-    - bank check
-    - credit card
-    - bank transfer
-    - cash
-    - refund
-    This Type of Note is not associated to a :model:`auth.User` or :model:`member.Club` .
-    """
-    note_name = models.CharField(
-        max_length=255,
-        unique=True,
-    )
-    
-    club = models.ForeignKey(
-        Club,
-        on_delete=models.PROTECT,
-        verbose_name=_("club"),
-    )
-
-    class Meta:
-        verbose_name = _("common note")
-        verbose_name_plural = _("common notes")
-
-    def __str__(self):
-        return self.note_name
-
-
 class Alias(models.Model):
     """
     points toward  a :model:`note.NoteUser` or :model;`note.NoteClub` instance.
diff --git a/templates/activity/activity_detail.html b/templates/activity/activity_detail.html
index 07c10a15..0ed3c719 100644
--- a/templates/activity/activity_detail.html
+++ b/templates/activity/activity_detail.html
@@ -66,7 +66,7 @@
             {% if "view_"|has_perm:activity %}
                 <a class="btn btn-primary btn-sm my-1" href="{% url 'activity:activity_update' pk=activity.pk %}"> {% trans "edit"|capfirst %}</a>
             {% endif %}
-            {% if activity.activity_type.can_invite %}
+            {% if activity.activity_type.can_invite and not activity_started %}
                 <a class="btn btn-primary btn-sm my-1" href="{% url 'activity:activity_invite' pk=activity.pk %}"> {% trans "Invite" %}</a>
             {% endif %}
         </div>