diff --git a/app/controllers/case_logs_controller.rb b/app/controllers/case_logs_controller.rb
index 18e9050c3..120a1ef1d 100644
--- a/app/controllers/case_logs_controller.rb
+++ b/app/controllers/case_logs_controller.rb
@@ -60,15 +60,19 @@ class CaseLogsController < ApplicationController
 
   def submit_form
     form = FormHandler.instance.get_form("2021_2022")
-    @case_log = CaseLog.find(params[:id])
-    page = form.get_page(params[:case_log][:page])
-    responses_for_page = responses_for_page(page)
-    if @case_log.update(responses_for_page) && @case_log.has_no_unresolved_soft_errors?
-      redirect_path = form.next_page_redirect_path(page, @case_log)
-      redirect_to(send(redirect_path, @case_log))
+    @case_log = current_user.case_logs.find_by(id: params[:id])
+    if @case_log
+      page = form.get_page(params[:case_log][:page])
+      responses_for_page = responses_for_page(page)
+      if @case_log.update(responses_for_page) && @case_log.has_no_unresolved_soft_errors?
+        redirect_path = form.next_page_redirect_path(page, @case_log)
+        redirect_to(send(redirect_path, @case_log))
+      else
+        subsection = form.subsection_for_page(page)
+        render "form/page", locals: { form: form, page: page, subsection: subsection.label }, status: :unprocessable_entity
+      end
     else
-      subsection = form.subsection_for_page(page)
-      render "form/page", locals: { form: form, page: page, subsection: subsection.label }, status: :unprocessable_entity
+      render file: "#{Rails.root}/public/404.html", status: 404
     end
   end
 
diff --git a/spec/requests/case_log_controller_spec.rb b/spec/requests/case_log_controller_spec.rb
index d8d52f61e..c5b4774ff 100644
--- a/spec/requests/case_log_controller_spec.rb
+++ b/spec/requests/case_log_controller_spec.rb
@@ -389,7 +389,14 @@ RSpec.describe CaseLogsController, type: :request do
   describe "Submit Form" do
     let(:user) { FactoryBot.create(:user) }
     let(:form) { Form.new("spec/fixtures/forms/test_form.json") }
-    let(:case_log) { FactoryBot.create(:case_log, :in_progress) }
+    let(:organisation) { user.organisation }
+    let(:case_log) do
+      FactoryBot.create(
+        :case_log,
+        owning_organisation: organisation,
+        managing_organisation: organisation,
+      )
+    end
     let(:page_id) { "person_1_age" }
     let(:params) do
       {
@@ -439,5 +446,26 @@ RSpec.describe CaseLogsController, type: :request do
         expect(case_log.age2).to be nil
       end
     end
+
+    context "case logs that are not owned or managed by your organisation" do
+      let(:answer) { 25 }
+      let(:other_organisation) { FactoryBot.create(:organisation) }
+      let(:unauthorized_case_log) do
+        FactoryBot.create(
+          :case_log,
+          owning_organisation: other_organisation,
+          managing_organisation: other_organisation,
+        )
+      end
+
+      before do
+        sign_in user
+        post "/case_logs/#{unauthorized_case_log.id}/form", params: params
+      end
+
+      it "does not let you post form answers to case logs you don't have access to" do
+        expect(response).to have_http_status(:not_found)
+      end
+    end
   end
 end