diff --git a/app/controllers/discourse_post_event/invitees_controller.rb b/app/controllers/discourse_post_event/invitees_controller.rb
index 59266b6e..b0052124 100644
--- a/app/controllers/discourse_post_event/invitees_controller.rb
+++ b/app/controllers/discourse_post_event/invitees_controller.rb
@@ -6,23 +6,50 @@ module DiscoursePostEvent
       event = Event.find(params[:post_id])
       guardian.ensure_can_see!(event.post)
 
-      event_invitees = event.invitees
+      filter = params[:filter].downcase if params[:filter]
 
-      if params[:filter]
+      event_invitees = event.invitees
+      event_invitees = event_invitees.with_status(params[:type].to_sym) if params[:type]
+
+      possible_invitees = []
+      if filter.present? && guardian.can_act_on_discourse_post_event?(event)
+        missing_users = event.missing_users(event_invitees.select(:user_id))
+
+        if filter
+          missing_users = missing_users.where("LOWER(username) LIKE :filter", filter: "%#{filter}%")
+
+          custom_order = <<~SQL
+            CASE
+              WHEN LOWER(username) = ? THEN 0
+              ELSE 1
+            END ASC,
+            LOWER(username) ASC
+          SQL
+
+          custom_order = ActiveRecord::Base.sanitize_sql_array([custom_order, filter])
+          missing_users = missing_users.order(custom_order).limit(10)
+        else
+          missing_users = missing_users.order(:username_lower).limit(10)
+        end
+
+        possible_invitees = missing_users
+      end
+
+      if filter
         event_invitees =
           event_invitees.joins(:user).where(
             "LOWER(users.username) LIKE :filter",
-            filter: "%#{params[:filter].downcase}%",
+            filter: "%#{filter}%",
           )
       end
 
-      event_invitees = event_invitees.with_status(params[:type].to_sym) if params[:type]
+      event_invitees = event_invitees.order(%i[status username_lower]).limit(200)
 
       render json:
-               ActiveModel::ArraySerializer.new(
-                 event_invitees.order(%i[status user_id]).limit(200),
-                 each_serializer: InviteeSerializer,
-               ).as_json
+               InviteeListSerializer.new(
+                 invitees: event_invitees,
+                 possible_invitees: possible_invitees,
+               )
     end
 
     def update
@@ -36,10 +63,20 @@ module DiscoursePostEvent
       event = Event.find(params[:post_id])
       guardian.ensure_can_see!(event.post)
 
-      raise Discourse::InvalidAccess if !event.can_user_update_attendance(current_user)
+      invitee_params = invitee_params(event)
 
-      invitee =
-        Invitee.create_attendance!(current_user.id, params[:post_id], invitee_params[:status])
+      user = current_user
+      if user_id = invitee_params[:user_id]
+        user = User.find(user_id.to_i)
+      end
+
+      raise Discourse::InvalidAccess if !event.can_user_update_attendance(user)
+
+      if current_user.id != user.id
+        raise Discourse::InvalidAccess if !guardian.can_act_on_discourse_post_event?(event)
+      end
+
+      invitee = Invitee.create_attendance!(user.id, params[:post_id], invitee_params[:status])
       render json: InviteeSerializer.new(invitee)
     end
 
@@ -54,8 +91,12 @@ module DiscoursePostEvent
 
     private
 
-    def invitee_params
-      params.require(:invitee).permit(:status)
+    def invitee_params(event = nil)
+      if event && guardian.can_act_on_discourse_post_event?(event)
+        params.require(:invitee).permit(:status, :user_id)
+      else
+        params.require(:invitee).permit(:status)
+      end
     end
   end
 end
diff --git a/app/models/discourse_post_event/event.rb b/app/models/discourse_post_event/event.rb
index 08d6a0ca..26a353c5 100644
--- a/app/models/discourse_post_event/event.rb
+++ b/app/models/discourse_post_event/event.rb
@@ -337,11 +337,19 @@ module DiscoursePostEvent
     end
 
     def missing_users(excluded_ids = self.invitees.select(:user_id))
-      User
-        .joins(:groups)
-        .where("groups.name" => self.raw_invitees)
-        .where.not(id: excluded_ids)
-        .distinct
+      users = User.real.activated.not_silenced.not_suspended.not_staged
+
+      if self.raw_invitees.present?
+        user_ids =
+          users
+            .joins(:groups)
+            .where("groups.name" => self.raw_invitees)
+            .where.not(id: excluded_ids)
+            .select(:id)
+        User.where(id: user_ids)
+      else
+        users.where.not(id: excluded_ids)
+      end
     end
 
     def update_with_params!(params)
diff --git a/app/serializers/discourse_post_event/invitee_list_serializer.rb b/app/serializers/discourse_post_event/invitee_list_serializer.rb
new file mode 100644
index 00000000..6c9f02bb
--- /dev/null
+++ b/app/serializers/discourse_post_event/invitee_list_serializer.rb
@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+module DiscoursePostEvent
+  class InviteeListSerializer < ApplicationSerializer
+    root false
+    attributes :meta
+    has_many :invitees, serializer: InviteeSerializer, embed: :objects
+
+    def invitees
+      object[:invitees]
+    end
+
+    def meta
+      {
+        possible_invitees:
+          ActiveModel::ArraySerializer.new(
+            possible_invitees,
+            each_serializer: BasicUserSerializer,
+            scope: scope,
+          ),
+      }
+    end
+
+    def include_meta?
+      possible_invitees.present?
+    end
+
+    def possible_invitees
+      object[:possible_invitees]
+    end
+  end
+end
diff --git a/assets/javascripts/discourse/components/modal/post-event-builder.hbs b/assets/javascripts/discourse/components/modal/post-event-builder.hbs
index a8f4395f..8f9ad853 100644
--- a/assets/javascripts/discourse/components/modal/post-event-builder.hbs
+++ b/assets/javascripts/discourse/components/modal/post-event-builder.hbs
@@ -15,8 +15,6 @@
         <DateTimeInputRange
           @from={{this.startsAt}}
           @to={{this.endsAt}}
-          @toTimeFirst={{true}}
-          @clearable={{true}}
           @timezone={{@model.event.timezone}}
           @onChange={{this.onChangeDates}}
         />
diff --git a/assets/javascripts/discourse/components/modal/post-event-invitees.gjs b/assets/javascripts/discourse/components/modal/post-event-invitees.gjs
new file mode 100644
index 00000000..7b0dd292
--- /dev/null
+++ b/assets/javascripts/discourse/components/modal/post-event-invitees.gjs
@@ -0,0 +1,166 @@
+import Component from "@glimmer/component";
+import { tracked } from "@glimmer/tracking";
+import { fn } from "@ember/helper";
+import { on } from "@ember/modifier";
+import { action } from "@ember/object";
+import { service } from "@ember/service";
+import { or } from "truth-helpers";
+import ConditionalLoadingSpinner from "discourse/components/conditional-loading-spinner";
+import DButton from "discourse/components/d-button";
+import DModal from "discourse/components/d-modal";
+import concatClass from "discourse/helpers/concat-class";
+import i18n from "discourse-common/helpers/i18n";
+import { debounce } from "discourse-common/utils/decorators";
+import I18n from "discourse-i18n";
+import renderInvitee from "../../helpers/render-invitee";
+import ToggleInvitees from "../toggle-invitees";
+
+export default class PostEventInvitees extends Component {
+  @service store;
+
+  @tracked invitees;
+  @tracked filter;
+  @tracked isLoading = false;
+  @tracked type = "going";
+  @tracked possibleInvitees = [];
+
+  constructor() {
+    super(...arguments);
+    this._fetchInvitees();
+  }
+
+  get hasPossibleInvitees() {
+    return this.possibleInvitees.length > 0;
+  }
+
+  get hasResults() {
+    return this.invitees?.length > 0 || this.hasPossibleInvitees;
+  }
+
+  get title() {
+    return I18n.t(
+      `discourse_calendar.discourse_post_event.invitees_modal.${
+        this.args.model.title || "title_invited"
+      }`
+    );
+  }
+
+  @action
+  toggleType(type) {
+    this.type = type;
+    this._fetchInvitees(this.filter);
+  }
+
+  @debounce(250)
+  onFilterChanged(event) {
+    this.filter = event.target.value;
+    this._fetchInvitees(this.filter);
+  }
+
+  @action
+  async removeInvitee(invitee) {
+    await invitee.destroyRecord();
+    this._fetchInvitees(this.filter);
+  }
+
+  @action
+  async addInvitee(user) {
+    const invitee = this.store.createRecord("discourse-post-event-invitee");
+    await invitee.save({
+      post_id: this.args.model.event.id,
+      user_id: user.id,
+      status: this.type,
+    });
+
+    this.invitees.pushObject(invitee);
+    this.possibleInvitees = this.possibleInvitees.filter(
+      (i) => i.id !== user.id
+    );
+  }
+
+  async _fetchInvitees(filter) {
+    try {
+      this.isLoading = true;
+      const invitees = await this.store.findAll(
+        "discourse-post-event-invitee",
+        {
+          filter,
+          post_id: this.args.model.event.id,
+          type: this.type,
+        }
+      );
+
+      this.possibleInvitees = invitees.resultSetMeta?.possible_invitees || [];
+      this.invitees = invitees;
+    } finally {
+      this.isLoading = false;
+    }
+  }
+  <template>
+    <DModal
+      @title={{this.title}}
+      @closeModal={{@closeModal}}
+      class={{concatClass
+        (or @model.extraClass "invited")
+        "post-event-invitees-modal"
+      }}
+    >
+      <:body>
+        <input
+          {{on "input" this.onFilterChanged}}
+          type="text"
+          placeholder={{i18n
+            "discourse_calendar.discourse_post_event.invitees_modal.filter_placeholder"
+          }}
+          class="filter"
+        />
+
+        <ToggleInvitees @viewType={{this.type}} @toggle={{this.toggleType}} />
+        <ConditionalLoadingSpinner @condition={{this.isLoading}}>
+          {{#if this.hasResults}}
+            <ul class="invitees">
+              {{#each this.invitees as |invitee|}}
+                <li class="invitee">
+                  {{renderInvitee invitee}}
+                  {{#if @model.event.can_act_on_discourse_post_event}}
+                    <DButton
+                      class="remove-invitee"
+                      @icon="trash-alt"
+                      @action={{fn this.removeInvitee invitee}}
+                      title={{i18n
+                        "discourse_calendar.discourse_post_event.invitees_modal.remove_invitee"
+                      }}
+                    />
+                  {{/if}}
+                </li>
+              {{/each}}
+            </ul>
+            {{#if this.hasPossibleInvitees}}
+              <ul class="possible-invitees">
+                {{#each this.possibleInvitees as |invitee|}}
+                  <li class="invitee">
+                    {{renderInvitee invitee}}
+                    <DButton
+                      class="add-invitee"
+                      @icon="plus"
+                      @action={{fn this.addInvitee invitee}}
+                      title={{i18n
+                        "discourse_calendar.discourse_post_event.invitees_modal.add_invitee"
+                      }}
+                    />
+                  </li>
+                {{/each}}
+              </ul>
+            {{/if}}
+          {{else}}
+            <p class="no-users">
+              {{i18n
+                "discourse_calendar.discourse_post_event.models.invitee.no_users"
+              }}
+            </p>
+          {{/if}}
+        </ConditionalLoadingSpinner>
+      </:body>
+    </DModal>
+  </template>
+}
diff --git a/assets/javascripts/discourse/components/modal/post-event-invitees.hbs b/assets/javascripts/discourse/components/modal/post-event-invitees.hbs
deleted file mode 100644
index e4782fd5..00000000
--- a/assets/javascripts/discourse/components/modal/post-event-invitees.hbs
+++ /dev/null
@@ -1,43 +0,0 @@
-<DModal
-  @title={{this.title}}
-  @closeModal={{@closeModal}}
-  class={{concat-class
-    (or @model.extraClass "invited")
-    "post-event-invitees-modal"
-  }}
->
-  <:body>
-    <Input
-      @value={{this.filter}}
-      {{on "input" this.onFilterChanged}}
-      class="filter"
-      placeholder={{i18n
-        "discourse_calendar.discourse_post_event.invitees_modal.filter_placeholder"
-      }}
-    />
-    <ToggleInvitees @viewType={{this.type}} @toggle={{this.toggleType}} />
-    <ConditionalLoadingSpinner @condition={{this.isLoading}}>
-      {{#if this.invitees}}
-        <ul class="invitees">
-          {{#each this.invitees as |invitee|}}
-            <li class="invitee">
-              {{render-invitee invitee}}
-              {{#if @model.event.can_act_on_discourse_post_event}}
-                <DButton
-                  @icon="trash-alt"
-                  @action={{fn this.removeInvitee invitee}}
-                />
-              {{/if}}
-            </li>
-          {{/each}}
-        </ul>
-      {{else}}
-        <p class="no-users">
-          {{i18n
-            "discourse_calendar.discourse_post_event.models.invitee.no_users"
-          }}
-        </p>
-      {{/if}}
-    </ConditionalLoadingSpinner>
-  </:body>
-</DModal>
\ No newline at end of file
diff --git a/assets/javascripts/discourse/components/modal/post-event-invitees.js b/assets/javascripts/discourse/components/modal/post-event-invitees.js
deleted file mode 100644
index 0c4f113b..00000000
--- a/assets/javascripts/discourse/components/modal/post-event-invitees.js
+++ /dev/null
@@ -1,63 +0,0 @@
-import Component from "@glimmer/component";
-import { tracked } from "@glimmer/tracking";
-import { action } from "@ember/object";
-import { inject as service } from "@ember/service";
-import { debounce } from "discourse-common/utils/decorators";
-import I18n from "discourse-i18n";
-
-export default class PostEventInvitees extends Component {
-  @service store;
-
-  @tracked invitees;
-  @tracked filter;
-  @tracked isLoading = false;
-  @tracked type = "going";
-
-  constructor() {
-    super(...arguments);
-    this._fetchInvitees();
-  }
-
-  get title() {
-    return I18n.t(
-      `discourse_calendar.discourse_post_event.invitees_modal.${
-        this.args.model.title || "title_invited"
-      }`
-    );
-  }
-
-  @action
-  toggleType(type) {
-    this.type = type;
-    this._fetchInvitees(this.filter);
-  }
-
-  @debounce(250)
-  onFilterChanged() {
-    this._fetchInvitees(this.filter);
-  }
-
-  @action
-  async removeInvitee(invitee) {
-    await invitee.destroyRecord();
-    this._fetchInvitees();
-  }
-
-  async _fetchInvitees(filter) {
-    try {
-      this.isLoading = true;
-      const invitees = await this.store.findAll(
-        "discourse-post-event-invitee",
-        {
-          filter,
-          post_id: this.args.model.event.id,
-          type: this.type,
-        }
-      );
-
-      this.invitees = invitees;
-    } finally {
-      this.isLoading = false;
-    }
-  }
-}
diff --git a/assets/javascripts/discourse/helpers/render-invitee.js b/assets/javascripts/discourse/helpers/render-invitee.js
index cde3cfaa..9a298b77 100644
--- a/assets/javascripts/discourse/helpers/render-invitee.js
+++ b/assets/javascripts/discourse/helpers/render-invitee.js
@@ -5,13 +5,14 @@ import { formatUsername } from "discourse/lib/utilities";
 import { htmlHelper } from "discourse-common/lib/helpers";
 
 export default htmlHelper((invitee) => {
-  const path = userPath(invitee.user.username);
+  const user = invitee.user || invitee;
+  const path = userPath(user.username);
   const template = `
-    <a href="${path}" data-user-card="${invitee.user.username}">
+    <a href="${path}" data-user-card="${user.username}">
       <span class="user">
-        ${renderAvatar(invitee.user, { imageSize: "medium" })}
+        ${renderAvatar(user, { imageSize: "medium" })}
         <span class="username">
-         ${formatUsername(invitee.user.username)}
+         ${formatUsername(user.username)}
         </span>
       </span>
     </a>
diff --git a/assets/stylesheets/common/discourse-post-event-invitees.scss b/assets/stylesheets/common/discourse-post-event-invitees.scss
index 3ee0f5e9..cf273662 100644
--- a/assets/stylesheets/common/discourse-post-event-invitees.scss
+++ b/assets/stylesheets/common/discourse-post-event-invitees.scss
@@ -8,7 +8,6 @@
   .loading-container {
     height: 40vh;
     overflow-y: scroll;
-    padding: 0 1em 9px 1em;
     .no-users {
       text-align: center;
       font-size: var(--font-up-1);
@@ -26,9 +25,11 @@
   }
   .filter {
     width: calc(100% - 2em);
-    margin: 1em;
+    margin-bottom: 1em;
   }
-  .invitees {
+
+  .invitees,
+  .possible-invitees {
     display: flex;
     margin: 0;
     flex-direction: column;
@@ -74,4 +75,9 @@
       }
     }
   }
+
+  .possible-invitees {
+    margin-top: 1em;
+    background-color: var(--primary-very-low);
+  }
 }
diff --git a/config/locales/client.en.yml b/config/locales/client.en.yml
index faad3e08..85152b8b 100644
--- a/config/locales/client.en.yml
+++ b/config/locales/client.en.yml
@@ -330,7 +330,7 @@ en:
           ends_in_duration: "Ends %{duration}"
         models:
           invitee:
-            no_users: "There are no users of this type."
+            no_users: "No users found"
             status:
               unknown: "Not interested"
               going: "Going"
@@ -365,9 +365,11 @@ en:
           close_event: "Close event"
           open_event: "Open event"
         invitees_modal:
-          title_invited: "List of RSVPed users"
+          title_invited: "Event Participation"
           title_participated: "List of users who participated"
           filter_placeholder: "Filter users"
+          remove_invitee: "Remove invitee from list"
+          add_invitee: "Add invitee to list"
         bulk_invite_modal:
           confirm: "confirm"
           text: "Upload CSV file"
diff --git a/spec/requests/invitees_controller_spec.rb b/spec/requests/invitees_controller_spec.rb
index 1593fed0..d336e2a6 100644
--- a/spec/requests/invitees_controller_spec.rb
+++ b/spec/requests/invitees_controller_spec.rb
@@ -46,6 +46,7 @@ module DiscoursePostEvent
         let(:invitee2) { Fabricate(:user, username: "Francisco", name: "Francisco") }
         let(:invitee3) { Fabricate(:user, username: "Frank", name: "Frank") }
         let(:invitee4) { Fabricate(:user, username: "Franchesca", name: "Franchesca") }
+        let!(:random_user) { Fabricate(:user, username: "Franny") }
         let(:post_event_1) do
           pe = Fabricate(:event, post: post_1)
           pe.create_invitees(
@@ -59,6 +60,28 @@ module DiscoursePostEvent
           pe
         end
 
+        context "when user is allowed to act on post event" do
+          it "returns users extra possible users when filtering the invitees by name" do
+            get "/discourse-post-event/events/#{post_event_1.id}/invitees.json",
+                params: {
+                  filter: "Fran",
+                  type: "going",
+                }
+
+            possible = response.parsed_body[:meta][:possible_invitees].map { |u| u[:username] }.sort
+            expect(possible).to eq(%w[Francisco Frank Franny])
+
+            get "/discourse-post-event/events/#{post_event_1.id}/invitees.json",
+                params: {
+                  filter: "",
+                  type: "going",
+                }
+
+            possible = response.parsed_body.dig(:meta, :possible_invitees)
+            expect(possible).to be_blank
+          end
+        end
+
         it "returns the correct amount of users when filtering the invitees by name" do
           get "/discourse-post-event/events/#{post_event_1.id}/invitees.json",
               params: {
@@ -241,6 +264,26 @@ module DiscoursePostEvent
         context "when the invitee is the event owner" do
           let(:post_event_2) { Fabricate(:event, post: post_1) }
 
+          it "allows inviting other users" do
+            user = Fabricate(:user)
+
+            post "/discourse-post-event/events/#{post_event_2.id}/invitees.json",
+                 params: {
+                   invitee: {
+                     status: "interested",
+                     user_id: user.id,
+                   },
+                 }
+
+            post_event_2.reload
+
+            expect(post_event_2.invitees.length).to eq(1)
+            invitee = post_event_2.invitees.first
+            expect(invitee.status).to eq(1)
+            expect(invitee.post_id).to eq(post_1.id)
+            expect(invitee.user_id).to eq(user.id)
+          end
+
           it "creates an invitee" do
             expect(post_event_2.invitees.length).to eq(0)
 
diff --git a/spec/system/post_event_spec.rb b/spec/system/post_event_spec.rb
index 792e4014..7b74bd16 100644
--- a/spec/system/post_event_spec.rb
+++ b/spec/system/post_event_spec.rb
@@ -2,6 +2,7 @@
 
 describe "Post event", type: :system do
   fab!(:admin)
+  fab!(:user) { Fabricate(:admin, username: "jane") }
   let(:composer) { PageObjects::Components::Composer.new }
 
   before do
@@ -39,5 +40,19 @@ describe "Post event", type: :system do
     page.find("#dialog-holder .btn-primary").click
 
     expect(page).to have_css(".discourse-post-event .status-and-creators .status.public")
+
+    page.find(".going-button").click
+    page.find(".event-invitees .show-all").click
+
+    page.find(".d-modal input.filter").fill_in(with: "jan")
+    page.find(".d-modal .add-invitee").click
+
+    topic_page = PageObjects::Pages::Topic.new
+
+    topic = Topic.find(topic_page.current_topic_id)
+
+    event = topic.posts.first.event
+
+    expect(event.invitees.count).to eq(2)
   end
 end