diff --git a/app/frontend/styles/_task-list.scss b/app/frontend/styles/_task-list.scss
index f8e2128dda..a739bc2453 100644
--- a/app/frontend/styles/_task-list.scss
+++ b/app/frontend/styles/_task-list.scss
@@ -52,3 +52,7 @@
     margin-bottom: 0;
   }
 }
+
+.app-red-text {
+  color: govuk-colour("red");
+}
diff --git a/app/helpers/collection_deadline_helper.rb b/app/helpers/collection_deadline_helper.rb
index 3c4f7e5027..de9c120755 100644
--- a/app/helpers/collection_deadline_helper.rb
+++ b/app/helpers/collection_deadline_helper.rb
@@ -61,12 +61,15 @@ def quarter_dates(year)
       first_quarter(year).merge(quarter: "Q1"),
       second_quarter(year).merge(quarter: "Q2"),
       third_quarter(year).merge(quarter: "Q3"),
+      fourth_quarter(year).merge(quarter: "Q4"),
     ]
   end
 
   def quarter_for_date(date: Time.zone.now)
-    quarters = quarter_dates(current_collection_start_year)
+    collection_start_year = collection_start_year_for_date(date)
+    return unless QUARTERLY_DEADLINES.key?(collection_start_year)
 
+    quarters = quarter_dates(collection_start_year)
     quarter = quarters.find { |q| date.between?(q[:start_date], q[:cutoff_date] + 1.day) }
 
     return unless quarter
diff --git a/app/helpers/tasklist_helper.rb b/app/helpers/tasklist_helper.rb
index ff52f40942..631f4d3151 100644
--- a/app/helpers/tasklist_helper.rb
+++ b/app/helpers/tasklist_helper.rb
@@ -2,6 +2,7 @@ module TasklistHelper
   include GovukLinkHelper
   include GovukVisuallyHiddenHelper
   include CollectionTimeHelper
+  include CollectionDeadlineHelper
 
   def breadcrumb_logs_title(log, current_user)
     log_type = log.lettings? ? "Lettings" : "Sales"
@@ -70,6 +71,22 @@ def tasklist_link_class(status)
     status == :cannot_start_yet ? "" : "govuk-task-list__item--with-link"
   end
 
+  def deadline_text(log)
+    return if log.completed?
+    return if log.startdate.nil?
+
+    log_quarter = quarter_for_date(date: log.startdate)
+    return if log_quarter.nil?
+
+    deadline_for_log = log_quarter.cutoff_date
+
+    if deadline_for_log.beginning_of_day >= Time.zone.today.beginning_of_day
+      "<p class=\"govuk-body\">Upcoming #{log_quarter.quarter} deadline: #{log_quarter.cutoff_date.strftime('%-d %B %Y')}.<p>".html_safe
+    else
+      "<p class=\"govuk-body app-red-text\"><strong>Overdue: #{log_quarter.quarter} deadline #{log_quarter.cutoff_date.strftime('%-d %B %Y')}.</strong></p>".html_safe
+    end
+  end
+
 private
 
   def breadcrumb_organisation(log)
diff --git a/app/views/logs/edit.html.erb b/app/views/logs/edit.html.erb
index 3859ca6db3..91d249362d 100644
--- a/app/views/logs/edit.html.erb
+++ b/app/views/logs/edit.html.erb
@@ -25,6 +25,7 @@
         <% end %>
       </p>
     <% elsif @log.status == "not_started" %>
+      <p class="govuk-body"><%= govuk_link_to "Guidance for submitting social housing lettings and sales data (opens in a new tab)", guidance_path, target: "#" %></p>
       <p class="govuk-body">This log has not been started.</p>
     <% elsif @log.status == "completed" %>
       <p class="govuk-body">
@@ -36,6 +37,7 @@
       </p>
     <% end %>
 
+    <%= deadline_text(@log) %>
     <%= render "tasklist" %>
 
     <%= edit_actions_for_log(@log, bulk_upload_filter_applied) %>
diff --git a/spec/helpers/tasklist_helper_spec.rb b/spec/helpers/tasklist_helper_spec.rb
index c5e1bd7846..dc683c7b28 100644
--- a/spec/helpers/tasklist_helper_spec.rb
+++ b/spec/helpers/tasklist_helper_spec.rb
@@ -204,4 +204,49 @@
       end
     end
   end
+
+  describe "deadline text" do
+    context "when log does not have a sale/start date" do
+      let(:log) { build(:sales_log, saledate: nil) }
+
+      it "returns nil" do
+        expect(deadline_text(log)).to be_nil
+      end
+    end
+
+    context "when log is completed" do
+      let(:log) { build(:sales_log, :completed, status: "completed") }
+
+      it "returns nil" do
+        expect(deadline_text(log)).to be_nil
+      end
+    end
+
+    context "when today is before the deadline for log with sale/start date" do
+      let(:log) { build(:sales_log, saledate: Time.zone.local(2025, 6, 1)) }
+
+      it "returns the deadline text" do
+        allow(Time.zone).to receive(:today).and_return(Time.zone.local(2025, 5, 7))
+        expect(deadline_text(log)).to include("Upcoming Q1 deadline: 11 July 2025.")
+      end
+    end
+
+    context "when today is the deadline for log with sale/start date" do
+      let(:log) { build(:sales_log, saledate: Time.zone.local(2025, 2, 1)) }
+
+      it "returns the overdue text" do
+        allow(Time.zone).to receive(:today).and_return(Time.zone.local(2025, 6, 6))
+        expect(deadline_text(log)).to include("Upcoming Q4 deadline: 6 June 2025.")
+      end
+    end
+
+    context "when today is after the deadline for log with sale/start date" do
+      let(:log) { build(:sales_log, saledate: Time.zone.local(2025, 2, 1)) }
+
+      it "returns the overdue text" do
+        allow(Time.zone).to receive(:today).and_return(Time.zone.local(2025, 6, 7))
+        expect(deadline_text(log)).to include("Overdue: Q4 deadline 6 June 2025.")
+      end
+    end
+  end
 end
diff --git a/spec/requests/lettings_logs_controller_spec.rb b/spec/requests/lettings_logs_controller_spec.rb
index 55cf3d573b..92683edb31 100644
--- a/spec/requests/lettings_logs_controller_spec.rb
+++ b/spec/requests/lettings_logs_controller_spec.rb
@@ -1155,6 +1155,21 @@
                 expect(lettings_log.status).to eq("completed")
                 expect(page).to have_link("review and make changes to this log", href: "/lettings-logs/#{lettings_log.id}/review")
               end
+
+              it "does not show guidance link" do
+                expect(page).not_to have_content("Guidance for submitting social housing lettings and sales data (opens in a new tab)")
+              end
+            end
+
+            context "and the log is not started" do
+              let(:lettings_log) { create(:lettings_log, status: "not_started", assigned_to: user) }
+
+              it "shows guidance link" do
+                allow(Time.zone).to receive(:now).and_return(lettings_log.form.edit_end_date - 1.day)
+                get lettings_log_path(lettings_log)
+                expect(lettings_log.status).to eq("not_started")
+                expect(page).to have_content("Guidance for submitting social housing lettings and sales data (opens in a new tab)")
+              end
             end
 
             context "with bulk_upload_id filter" do
diff --git a/spec/requests/sales_logs_controller_spec.rb b/spec/requests/sales_logs_controller_spec.rb
index d8209fa1d1..e85ecb813e 100644
--- a/spec/requests/sales_logs_controller_spec.rb
+++ b/spec/requests/sales_logs_controller_spec.rb
@@ -866,6 +866,7 @@
     context "when viewing a sales log" do
       let(:headers) { { "Accept" => "text/html" } }
       let(:completed_sales_log) { FactoryBot.create(:sales_log, :completed, owning_organisation: user.organisation, assigned_to: user) }
+      let(:not_started_sales_log) { FactoryBot.create(:sales_log, owning_organisation: user.organisation, assigned_to: user) }
 
       before do
         sign_in user
@@ -956,6 +957,16 @@
           expect(page).to have_content("This log is from the 2021 to 2022 collection window, which is now closed.")
         end
       end
+
+      it "does not show guidance link" do
+        get "/sales-logs/#{completed_sales_log.id}", headers:, params: {}
+        expect(page).not_to have_content("Guidance for submitting social housing lettings and sales data (opens in a new tab)")
+      end
+
+      it "shows guidance link for not_started log" do
+        get "/sales-logs/#{not_started_sales_log.id}", headers:, params: {}
+        expect(page).to have_content("Guidance for submitting social housing lettings and sales data (opens in a new tab)")
+      end
     end
 
     context "when requesting CSV download" do