diff --git a/spec/services/bulk_upload/lettings/validator_spec.rb b/spec/services/bulk_upload/lettings/validator_spec.rb
index d36103d5a..12d53136e 100644
--- a/spec/services/bulk_upload/lettings/validator_spec.rb
+++ b/spec/services/bulk_upload/lettings/validator_spec.rb
@@ -5,38 +5,97 @@ RSpec.describe BulkUpload::Lettings::Validator do
 
   let(:organisation) { create(:organisation, old_visible_id: "3") }
   let(:user) { create(:user, organisation:) }
+  let(:log) { build(:lettings_log, :completed) }
   let(:bulk_upload) { create(:bulk_upload, user:, year: 2022) }
   let(:path) { file.path }
   let(:file) { Tempfile.new }
 
   describe "validations" do
+    let(:bulk_upload) { create(:bulk_upload, user:, year: 2023) }
+
     context "when file is empty" do
       it "is not valid" do
         expect(validator).not_to be_valid
       end
     end
 
-    context "when file has too many columns" do
+    context "when file has no headers and too many columns" do
       before do
-        file.write("a," * 136)
+        file.write(("a" * 143).chars.join(","))
         file.write("\n")
         file.rewind
       end
 
       it "is not valid" do
         expect(validator).not_to be_valid
+        expect(validator.errors["base"]).to eql(["too many columns, please ensure you have used the correct template"])
       end
     end
 
-    context "when file has too few columns" do
+    context "when file has no headers and doesn't have too many columns" do
       before do
-        file.write("a," * 132)
+        file.write(("a" * 142).chars.join(","))
         file.write("\n")
         file.rewind
       end
 
+      it "is valid" do
+        expect(validator).to be_valid
+      end
+    end
+
+    context "when file has extra invalid headers" do
+      let(:seed) { rand }
+      let(:log_to_csv) { BulkUpload::LogToCsv.new(log:) }
+      let(:field_numbers) { log_to_csv.default_2023_field_numbers + %w[invalid_field_number] }
+      let(:field_values) { log_to_csv.to_2023_row + %w[value_for_invalid_field_number] }
+
+      before do
+        file.write(log_to_csv.custom_2023_field_numbers_row(seed:, field_numbers:))
+        file.write(log_to_csv.to_custom_2023_csv_row(seed:, field_values:))
+        file.rewind
+      end
+
+      it "is valid" do
+        expect(validator).to be_valid
+      end
+    end
+
+    context "when file has too few valid headers" do
+      let(:seed) { rand }
+      let(:log_to_csv) { BulkUpload::LogToCsv.new(log:) }
+      let(:field_numbers) { log_to_csv.default_2023_field_numbers }
+      let(:field_values) { log_to_csv.to_2023_row }
+
+      before do
+        field_numbers.delete_at(20)
+        field_values.delete_at(20)
+        file.write(log_to_csv.custom_2023_field_numbers_row(seed:, field_numbers:))
+        file.write(log_to_csv.to_custom_2023_csv_row(seed:, field_values:))
+        file.rewind
+      end
+
+      it "is not valid" do
+        expect(validator).not_to be_valid
+        expect(validator.errors["base"]).to eql(["incorrect number of fields, please ensure you have used the correct template"])
+      end
+    end
+
+    context "when file has too many valid headers" do
+      let(:seed) { rand }
+      let(:log_to_csv) { BulkUpload::LogToCsv.new(log:) }
+      let(:field_numbers) { log_to_csv.default_2023_field_numbers + %w[23] }
+      let(:field_values) { log_to_csv.to_2023_row + %w[value] }
+
+      before do
+        file.write(log_to_csv.custom_2023_field_numbers_row(seed:, field_numbers:))
+        file.write(log_to_csv.to_custom_2023_csv_row(seed:, field_values:))
+        file.rewind
+      end
+
       it "is not valid" do
         expect(validator).not_to be_valid
+        expect(validator.errors["base"]).to eql(["incorrect number of fields, please ensure you have used the correct template"])
       end
     end