diff --git a/app/models/immunisation_import_row.rb b/app/models/immunisation_import_row.rb
index f92d144df6..3ea6102189 100644
--- a/app/models/immunisation_import_row.rb
+++ b/app/models/immunisation_import_row.rb
@@ -52,6 +52,7 @@ class ImmunisationImportRow
   validates :time_of_vaccination,
             presence: true,
             if: -> { @data["TIME_OF_VACCINATION"]&.strip.present? }
+  validate :session_date_exists
 
   CARE_SETTING_SCHOOL = 1
   CARE_SETTING_COMMUNITY = 2
@@ -323,8 +324,6 @@ def administered_at
   end
 
   def location
-    return unless valid?
-
     @location ||=
       if school && (care_setting.nil? || care_setting == CARE_SETTING_SCHOOL)
         school
@@ -334,12 +333,10 @@ def location
   end
 
   def school
-    return unless valid?
-
     @school ||=
       if school_urn != SCHOOL_URN_HOME_EDUCATED &&
            school_urn != SCHOOL_URN_UNKNOWN
-        Location.find_by!(urn: school_urn)
+        Location.find_by(urn: school_urn)
       end
   end
 
@@ -407,6 +404,19 @@ def date_of_birth_in_a_valid_year_group
     end
   end
 
+  def session_date_exists
+    return if date_of_vaccination.nil? || location.nil?
+    return if academic_year != Date.current.academic_year
+
+    unless Session.has_date(date_of_vaccination).exists?(
+             organisation:,
+             location:,
+             academic_year:
+           )
+      errors.add(:date_of_vaccination, :inclusion)
+    end
+  end
+
   def existing_patients
     if patient_first_name.blank? || patient_last_name.blank? ||
          patient_date_of_birth.nil? || patient_postcode.blank?
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 0e4c81fc72..f25dd5c397 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -235,6 +235,7 @@ en:
               blank: Enter a date in the correct format.
               greater_than_or_equal_to: The vaccination date is outside the programme. Enter a date after the programme started.
               less_than_or_equal_to: The vaccination date is outside the programme. Enter a date before today.
+              inclusion: Enter a date for a current session
             time_of_vaccination:
               blank: Enter a time in the correct format.
             vaccine_given:
diff --git a/spec/features/import_vaccination_records_spec.rb b/spec/features/import_vaccination_records_spec.rb
index 2888792a71..544e11197a 100644
--- a/spec/features/import_vaccination_records_spec.rb
+++ b/spec/features/import_vaccination_records_spec.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 describe "Immunisation imports" do
-  around { |example| travel_to(Date.new(2024, 5, 20)) { example.run } }
+  around { |example| travel_to(Date.new(2025, 5, 20)) { example.run } }
 
   scenario "User uploads a file, views cohort and vaccination records" do
     given_i_am_signed_in
diff --git a/spec/models/immunisation_import_row_spec.rb b/spec/models/immunisation_import_row_spec.rb
index f1b66c1966..f044b90edf 100644
--- a/spec/models/immunisation_import_row_spec.rb
+++ b/spec/models/immunisation_import_row_spec.rb
@@ -132,6 +132,26 @@
       end
     end
 
+    context "when date doesn't match an existing session" do
+      subject(:errors) { immunisation_import_row.errors[:date_of_vaccination] }
+
+      before { immunisation_import_row.valid? }
+
+      context "when importing for the current academic year" do
+        let(:data) do
+          { "DATE_OF_VACCINATION" => "#{Date.current.academic_year}0901" }
+        end
+
+        it { should include(/current session/) }
+      end
+
+      context "when importing for a different academic year" do
+        let(:data) { { "DATE_OF_VACCINATION" => "20220101" } }
+
+        it { should be_empty }
+      end
+    end
+
     context "with an invalid time of vaccination" do
       let(:data) { { "TIME_OF_VACCINATION" => "abc" } }
 
@@ -528,7 +548,7 @@
     context "without data" do
       let(:data) { {} }
 
-      it { should be_nil }
+      it { should eq("Unknown") }
     end
 
     context "with a school" do