diff --git a/app/models/case_log.rb b/app/models/case_log.rb
index 68cbef3ac..5e78990f3 100644
--- a/app/models/case_log.rb
+++ b/app/models/case_log.rb
@@ -186,6 +186,10 @@ class CaseLog < ApplicationRecord
     previous_la_known == 1
   end
 
+  def tshortfall_unknown?
+    tshortfall_known == 1
+  end
+
   def is_secure_tenancy?
     # 1: Secure (including flexible)
     tenancy == 1
@@ -367,6 +371,10 @@ class CaseLog < ApplicationRecord
     "#{soft_value_for_period(soft_max)} #{SUFFIX_FROM_PERIOD[period].presence || 'every week'}"
   end
 
+  def optional_fields
+    OPTIONAL_FIELDS + dynamically_not_required
+  end
+
 private
 
   PIO = Postcodes::IO.new
@@ -425,7 +433,8 @@ private
 
   def dynamically_not_required
     previous_la_known_field = postcode_known? ? %w[previous_la_known] : []
-    ((form.invalidated_questions(self) + form.readonly_questions).map(&:id) + previous_la_known_field).uniq
+    tshortfall_field = tshortfall_unknown? ? %w[tshortfall] : []
+    previous_la_known_field + tshortfall_field
   end
 
   def set_derived_fields!
@@ -458,6 +467,7 @@ private
       end
     end
     self.has_benefits = get_has_benefits
+    self.tshortfall_known = 0 if tshortfall
     self.wtshortfall = if tshortfall && receives_housing_related_benefits?
                          weekly_value(tshortfall)
                        end
@@ -622,13 +632,9 @@ private
   end
 
   def all_fields_nil?
-    init_fields = %w[owning_organisation_id managing_organisation_id]
-    fields = mandatory_fields.difference(init_fields)
-    fields.none? { |field| public_send(field).present? if respond_to?(field) }
-  end
-
-  def mandatory_fields
-    form.questions.map(&:id).difference(OPTIONAL_FIELDS, dynamically_not_required)
+    not_started_statuses = %i[not_started cannot_start_yet]
+    subsection_statuses = form.subsections.map { |subsection| subsection.status(self) }.uniq
+    subsection_statuses.all? { |status| not_started_statuses.include?(status) }
   end
 
   def age_refused?
diff --git a/app/models/form.rb b/app/models/form.rb
index e339f6fdc..7f48d7d4c 100644
--- a/app/models/form.rb
+++ b/app/models/form.rb
@@ -124,8 +124,8 @@ class Form
   end
 
   def enabled_page_questions(case_log)
-    pages_that_are_routed_to = pages.select { |p| p.routed_to?(case_log) }
-    pages_that_are_routed_to.flat_map(&:questions) || []
+    pages_that_are_routed_to_or_derived = pages.select { |p| p.routed_to?(case_log) || p.derived }
+    pages_that_are_routed_to_or_derived.flat_map(&:questions) || []
   end
 
   def invalidated_conditional_questions(case_log)
@@ -155,6 +155,8 @@ class Form
     return true unless depends_on
 
     depends_on.any? do |conditions_set|
+      return false unless conditions_set
+
       conditions_set.all? do |question, value|
         if value.is_a?(Hash) && value.key?("operator")
           operator = value["operator"]
diff --git a/app/models/form/page.rb b/app/models/form/page.rb
index 155f85d20..7822c2b68 100644
--- a/app/models/form/page.rb
+++ b/app/models/form/page.rb
@@ -1,5 +1,5 @@
 class Form::Page
-  attr_accessor :id, :header, :description, :questions,
+  attr_accessor :id, :header, :description, :questions, :derived,
                 :depends_on, :title_text, :informative_text, :subsection, :hide_subsection_label
 
   def initialize(id, hsh, subsection)
@@ -8,6 +8,7 @@ class Form::Page
     @description = hsh["description"]
     @questions = hsh["questions"].map { |q_id, q| Form::Question.new(q_id, q, self) }
     @depends_on = hsh["depends_on"]
+    @derived = hsh["derived"]
     @title_text = hsh["title_text"]
     @informative_text = hsh["informative_text"]
     @hide_subsection_label = hsh["hide_subsection_label"]
diff --git a/app/models/form/subsection.rb b/app/models/form/subsection.rb
index 95216c9d4..20b65ad9f 100644
--- a/app/models/form/subsection.rb
+++ b/app/models/form/subsection.rb
@@ -31,7 +31,7 @@ class Form::Subsection
     end
 
     qs = applicable_questions(case_log)
-    qs_optional_removed = qs.reject { |q| CaseLog::OPTIONAL_FIELDS.include?(q.id) }
+    qs_optional_removed = qs.reject { |q| case_log.optional_fields.include?(q.id) }
     return :not_started if qs.all? { |question| case_log[question.id].blank? || question.read_only? }
     return :completed if qs_optional_removed.all? { |question| question.completed?(case_log) }
 
diff --git a/app/services/imports/case_logs_import_service.rb b/app/services/imports/case_logs_import_service.rb
index cf7cd4cee..56ccbd8d8 100644
--- a/app/services/imports/case_logs_import_service.rb
+++ b/app/services/imports/case_logs_import_service.rb
@@ -125,8 +125,9 @@ module Imports
       attributes["supcharg"] = safe_string_as_decimal(xml_doc, "Q18aiv")
       attributes["tcharge"] = safe_string_as_decimal(xml_doc, "Q18av")
 
+      attributes["hbrentshortfall"] = unsafe_string_as_integer(xml_doc, "Q18d")
       attributes["tshortfall"] = safe_string_as_decimal(xml_doc, "Q18dyes")
-      attributes["hbrentshortfall"] = hbshortfall(xml_doc, attributes)
+      attributes["tshortfall_known"] = tshortfall_known?(xml_doc, attributes)
 
       attributes["voiddate"] = compose_date(xml_doc, "VDAY", "VMONTH", "VYEAR")
       attributes["mrcdate"] = compose_date(xml_doc, "MRCDAY", "MRCMONTH", "MRCYEAR")
@@ -214,7 +215,7 @@ module Imports
     end
 
     def fields_not_present_in_softwire_data
-      %w[majorrepairs illness_type_0]
+      %w[majorrepairs illness_type_0 tshortfall_known]
     end
 
     def check_status_completed(case_log, previous_status)
@@ -520,14 +521,11 @@ module Imports
       ((2..8).map { |x| string_or_nil(xml_doc, "P#{x}Rel") } + [string_or_nil(xml_doc, "P1Sex")]).compact
     end
 
-    def hbshortfall(xml_doc, attributes)
-      shortfall = unsafe_string_as_integer(xml_doc, "Q18d")
-      if attributes["tshortfall"].blank? && shortfall == 1 && overridden?(xml_doc, "xmlns", "Q18dyes")
-        # If they have said there is a shortfall but then not entered one, and that has been
-        # manually overridden we instead infer that they actually didn't know whether there is a shortfall.
-        3
+    def tshortfall_known?(xml_doc, attributes)
+      if attributes["tshortfall"].blank? && attributes["hbrentshortfall"] == 1 && overridden?(xml_doc, "xmlns", "Q18dyes")
+        1
       else
-        shortfall
+        0
       end
     end
   end
diff --git a/config/forms/2021_2022.json b/config/forms/2021_2022.json
index 8715e1a46..1fe6bfb0d 100644
--- a/config/forms/2021_2022.json
+++ b/config/forms/2021_2022.json
@@ -5717,6 +5717,29 @@
                 }
               ]
             },
+            "outstanding_amount_known": {
+              "header": "",
+              "description": "",
+              "questions": {
+                "tshortfall_known": {
+                  "check_answer_label": "",
+                  "header": "",
+                  "hint_text": "",
+                  "hidden_in_check_answers": true,
+                  "type": "radio",
+                  "answer_options": {
+                    "0": {
+                      "value": "Yes"
+                    },
+                    "1": {
+                      "value": "No"
+                    }
+                  }
+                }
+              },
+              "derived": true,
+              "depends_on": [false]
+            },
             "outstanding_amount": {
               "header": "",
               "description": "",
diff --git a/config/forms/2022_2023.json b/config/forms/2022_2023.json
index 513a67e15..f445ebe7c 100644
--- a/config/forms/2022_2023.json
+++ b/config/forms/2022_2023.json
@@ -5740,6 +5740,29 @@
                 }
               ]
             },
+            "outstanding_amount_known": {
+              "header": "",
+              "description": "",
+              "questions": {
+                "tshortfall_known": {
+                  "check_answer_label": "",
+                  "header": "",
+                  "hint_text": "",
+                  "hidden_in_check_answers": true,
+                  "type": "radio",
+                  "answer_options": {
+                    "0": {
+                      "value": "Yes"
+                    },
+                    "1": {
+                      "value": "No"
+                    }
+                  }
+                }
+              },
+              "derived": true,
+              "depends_on": [false]
+            },
             "outstanding_amount": {
               "header": "",
               "description": "",
diff --git a/db/migrate/20220510091620_add_tshortfall_known_case_logs.rb b/db/migrate/20220510091620_add_tshortfall_known_case_logs.rb
new file mode 100644
index 000000000..1059324ba
--- /dev/null
+++ b/db/migrate/20220510091620_add_tshortfall_known_case_logs.rb
@@ -0,0 +1,5 @@
+class AddTshortfallKnownCaseLogs < ActiveRecord::Migration[7.0]
+  def change
+    add_column :case_logs, :tshortfall_known, :integer
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index ddab93cfe..ba9001e74 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 2022_05_06_092350) do
+ActiveRecord::Schema[7.0].define(version: 2022_05_10_091620) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
@@ -222,6 +222,7 @@ ActiveRecord::Schema[7.0].define(version: 2022_05_06_092350) do
     t.integer "joint"
     t.bigint "created_by_id"
     t.integer "illness_type_0"
+    t.integer "tshortfall_known"
     t.index ["created_by_id"], name: "index_case_logs_on_created_by_id"
     t.index ["managing_organisation_id"], name: "index_case_logs_on_managing_organisation_id"
     t.index ["old_id"], name: "index_case_logs_on_old_id", unique: true
diff --git a/spec/fixtures/exports/case_logs.xml b/spec/fixtures/exports/case_logs.xml
index 00dfd5243..66795680e 100644
--- a/spec/fixtures/exports/case_logs.xml
+++ b/spec/fixtures/exports/case_logs.xml
@@ -164,6 +164,7 @@
     <joint/>
     <created_by_id>{created_by_id}</created_by_id>
     <illness_type_0/>
+    <tshortfall_known>0</tshortfall_known>
     <providertype>1</providertype>
   </form>
 </forms>
diff --git a/spec/fixtures/forms/2022_2023.json b/spec/fixtures/forms/2022_2023.json
index 8d856aa1c..e9fcb6990 100644
--- a/spec/fixtures/forms/2022_2023.json
+++ b/spec/fixtures/forms/2022_2023.json
@@ -94,6 +94,29 @@
                     "width": 10
                   }
                 }
+              },
+              "outstanding_amount_known": {
+                "header": "",
+                "description": "",
+                "questions": {
+                  "tshortfall_known": {
+                    "check_answer_label": "",
+                    "header": "",
+                    "hint_text": "",
+                    "hidden_in_check_answers": true,
+                    "type": "radio",
+                    "answer_options": {
+                      "0": {
+                        "value": "Yes"
+                      },
+                      "1": {
+                        "value": "No"
+                      }
+                    }
+                  }
+                },
+                "derived": true,
+                "depends_on": [false]
               }
             }
           }
diff --git a/spec/models/case_log_spec.rb b/spec/models/case_log_spec.rb
index 7fdbd6381..f420ade1c 100644
--- a/spec/models/case_log_spec.rb
+++ b/spec/models/case_log_spec.rb
@@ -1660,6 +1660,26 @@ RSpec.describe CaseLog do
         expect(relet_case_log["newprop"]).to eq(2)
       end
     end
+
+    context "when a total shortfall is provided" do
+      it "derives that tshortfall is known" do
+        case_log.update!({ tshortfall: 10 })
+        record_from_db = ActiveRecord::Base.connection.execute("select tshortfall_known from case_logs where id=#{case_log.id}").to_a[0]
+        expect(record_from_db["tshortfall_known"]).to eq(0)
+        expect(case_log["tshortfall_known"]).to eq(0)
+      end
+    end
+  end
+
+  describe "optional fields" do
+    let(:case_log) { FactoryBot.create(:case_log) }
+
+    context "when tshortfall is marked as not known" do
+      it "makes tshortfall optional" do
+        case_log.update!({ tshortfall: nil, tshortfall_known: 1 })
+        expect(case_log.optional_fields).to include("tshortfall")
+      end
+    end
   end
 
   describe "resetting invalidated fields" do
@@ -1751,6 +1771,32 @@ RSpec.describe CaseLog do
     end
   end
 
+  describe "tshortfall_unknown?" do
+    context "when tshortfall is nil" do
+      let(:case_log) { FactoryBot.create(:case_log, :in_progress, tshortfall_known: nil) }
+
+      it "returns false" do
+        expect(case_log.tshortfall_unknown?).to be false
+      end
+    end
+
+    context "when tshortfall is No" do
+      let(:case_log) { FactoryBot.create(:case_log, :in_progress, tshortfall_known: 1) }
+
+      it "returns false" do
+        expect(case_log.tshortfall_unknown?).to be true
+      end
+    end
+
+    context "when tshortfall is Yes" do
+      let(:case_log) { FactoryBot.create(:case_log, :in_progress, tshortfall_known: 0) }
+
+      it "returns false" do
+        expect(case_log.tshortfall_unknown?).to be false
+      end
+    end
+  end
+
   describe "paper trail" do
     let(:case_log) { FactoryBot.create(:case_log, :in_progress) }
 
diff --git a/spec/models/form_spec.rb b/spec/models/form_spec.rb
index 43628ab78..08cd1718e 100644
--- a/spec/models/form_spec.rb
+++ b/spec/models/form_spec.rb
@@ -190,5 +190,17 @@ RSpec.describe Form, type: :model do
         expect(form.invalidated_page_questions(case_log).map(&:id).uniq).to eq(expected_invalid)
       end
     end
+
+    context "when a page is marked as `derived` and `depends_on: false`" do
+      let(:case_log) { FactoryBot.build(:case_log, :in_progress, startdate: Time.utc(2023, 2, 2, 10, 36, 49)) }
+
+      it "does not count it's questions as invalidated" do
+        expect(form.enabled_page_questions(case_log).map(&:id).uniq).to include("tshortfall_known")
+      end
+
+      it "does not route to the page" do
+        expect(form.invalidated_pages(case_log).map(&:id)).to include("outstanding_amount_known")
+      end
+    end
   end
 end