diff --git a/app/controllers/form_controller.rb b/app/controllers/form_controller.rb
index df924665a..656e0ab6e 100644
--- a/app/controllers/form_controller.rb
+++ b/app/controllers/form_controller.rb
@@ -7,11 +7,16 @@ class FormController < ApplicationController
     if @case_log
       @page = @case_log.form.get_page(params[:case_log][:page])
       responses_for_page = responses_for_page(@page)
-      if @case_log.update(responses_for_page)
+      mandatory_questions_with_no_response = mandatory_questions_with_no_response(responses_for_page)
+
+      if mandatory_questions_with_no_response.empty? && @case_log.update(responses_for_page)
         session[:errors] = nil
         redirect_to(successful_redirect_path)
       else
         redirect_path = "case_log_#{@page.id}_path"
+        mandatory_questions_with_no_response.map do |question|
+          @case_log.errors.add question.id.to_sym, I18n.t("validations.not_answered", question: question.display_label.downcase)
+        end
         session[:errors] = @case_log.errors.to_json
         Rails.logger.info "User triggered validation(s) on: #{@case_log.errors.map(&:attribute).join(', ')}"
         redirect_to(send(redirect_path, @case_log))
@@ -120,4 +125,13 @@ private
     redirect_path = @case_log.form.next_page_redirect_path(@page, @case_log, current_user)
     send(redirect_path, @case_log)
   end
+
+  def mandatory_questions_with_no_response(responses_for_page)
+    @page.questions.select do |question| 
+      (responses_for_page[question.id].nil? || responses_for_page[question.id].empty?) && 
+        CaseLog::OPTIONAL_FIELDS.exclude?(question.id) && 
+          @page.subsection.applicable_questions(@case_log).map(&:id).include?(question.id) 
+    end
+  end
 end
+
diff --git a/app/models/form/question.rb b/app/models/form/question.rb
index 35d776e6c..3d2f7a8a3 100644
--- a/app/models/form/question.rb
+++ b/app/models/form/question.rb
@@ -173,6 +173,10 @@ class Form::Question
     type == "radio" && RADIO_REFUSED_VALUE[id.to_sym]&.include?(value)
   end
 
+  def display_label 
+    check_answer_label || header || id.humanize
+  end
+
 private
 
   def selected_answer_option_is_derived?(case_log)
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 0b76d9abf..37d04a013 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -42,6 +42,7 @@ en:
     organisation:
       name_missing: "Enter the organisation’s name"
       provider_type_missing: "Select the organisation’s type"
+    not_answered: "You must answer %{question}"
 
     other_field_missing: "If %{main_field_label} is other then %{other_field_label} must be provided"
     other_field_not_required: "%{other_field_label} must not be provided if %{main_field_label} was not other"
diff --git a/spec/features/form/form_navigation_spec.rb b/spec/features/form/form_navigation_spec.rb
index b2af0d190..b572e8783 100644
--- a/spec/features/form/form_navigation_spec.rb
+++ b/spec/features/form/form_navigation_spec.rb
@@ -56,17 +56,11 @@ RSpec.describe "Form Navigation" do
       pages = question_answers.map { |_key, val| val[:path] }
       pages[0..-2].each_with_index do |val, index|
         visit("/logs/#{id}/#{val}")
-        click_button("Save and continue")
+        click_link("Skip for now")
         expect(page).to have_current_path("/logs/#{id}/#{pages[index + 1]}")
       end
     end
 
-    it "a question page has a link allowing you to cancel your input and return to the check answers page" do
-      visit("logs/#{id}/tenant-code-test?referrer=check_answers")
-      click_link(text: "Cancel")
-      expect(page).to have_current_path("/logs/#{id}/setup/check-answers")
-    end
-
     it "a question page has a Skip for now link that lets you move on to the next question without inputting anything" do
       visit("logs/#{empty_case_log.id}/tenant-code-test")
       click_link(text: "Skip for now")
@@ -116,4 +110,57 @@ RSpec.describe "Form Navigation" do
       end
     end
   end
+
+  describe "Editing a log" do
+    it "a question page has a link allowing you to cancel your input and return to the check answers page" do
+      visit("logs/#{id}/tenant-code-test?referrer=check_answers")
+      click_link(text: "Cancel")
+      expect(page).to have_current_path("/logs/#{id}/setup/check-answers")
+    end
+
+    context "when clicking save and continue on a mandatory question with no input" do
+      let(:id) { empty_case_log.id }
+
+      it "shows a validation error on radio questions" do
+        visit("/logs/#{id}/renewal")
+        click_button("Save and continue")
+        expect(page).to have_selector("#error-summary-title")
+        expect(page).to have_selector("#case-log-renewal-error")
+        expect(page).to have_title("Error")
+      end
+
+      it "shows a validation error on date questions" do
+        visit("/logs/#{id}/tenancy-start-date")
+        click_button("Save and continue")
+        expect(page).to have_selector("#error-summary-title")
+        expect(page).to have_selector("#case-log-startdate-error")
+        expect(page).to have_title("Error")
+      end
+
+      context "when the page has a main and conditional question" do 
+        context "when the conditional question is required but not answered" do
+          xit "shows a validation error for the conditional question", js: true do
+            visit("/logs/#{id}/armed-forces")
+            choose("case-log-armedforces-1-field", allow_label_click: true)
+            click_button("Save and continue")
+            expect(page).to have_selector("#error-summary-title")
+            expect(page).to have_selector("#case-log-leftreg-error")
+            expect(page).to have_title("Error")
+          end
+        end 
+      end
+    end
+
+    context "when clicking save and continue on an optional question with no input" do
+      let(:id) { empty_case_log.id }
+
+      it "does not show a validation error" do
+        visit("/logs/#{id}/tenant-code")
+        click_button("Save and continue")
+        expect(page).not_to have_selector("#error-summary-title")
+        expect(page).not_to have_title("Error")
+        expect(page).to have_current_path("/logs/#{id}/property-reference")
+      end
+    end
+  end
 end