diff --git a/lib/tasks/correct_ppcodenk_values.rake b/lib/tasks/correct_ppcodenk_values.rake
new file mode 100644
index 000000000..86c678fc0
--- /dev/null
+++ b/lib/tasks/correct_ppcodenk_values.rake
@@ -0,0 +1,6 @@
+desc "Alter ppcodenk values for non imported lettings logs in the database"
+task correct_ppcodenk_values: :environment do
+  LettingsLog.where.not(ppcodenk: nil).find_each do |log|
+    log.update_columns(ppcodenk: log.ppcodenk == 1 ? 0 : 1)
+  end
+end
diff --git a/spec/lib/tasks/correct_ppcodenk_values_spec.rb b/spec/lib/tasks/correct_ppcodenk_values_spec.rb
new file mode 100644
index 000000000..fabfd05f3
--- /dev/null
+++ b/spec/lib/tasks/correct_ppcodenk_values_spec.rb
@@ -0,0 +1,67 @@
+require "rails_helper"
+require "rake"
+
+RSpec.describe "correct_ppcodenk_values" do
+  describe ":correct_ppcodenk_values", type: :task do
+    subject(:task) { Rake::Task["correct_ppcodenk_values"] }
+
+    before do
+      Rake.application.rake_require("tasks/correct_ppcodenk_values")
+      Rake::Task.define_task(:environment)
+      task.reenable
+    end
+
+    context "when the rake task is run" do
+      let!(:lettings_log) { create(:lettings_log, :completed) }
+
+      it "updates lettings logs with ppcodenk 0 to have ppcodenk 1" do
+        lettings_log.update!(ppcodenk: 0)
+        task.invoke
+        expect(lettings_log.reload.ppcodenk).to eq(1)
+      end
+
+      it "updates lettings logs with ppcodenk 1 to have ppcodenk 0" do
+        lettings_log.update!(ppcodenk: 1)
+        task.invoke
+        expect(lettings_log.reload.ppcodenk).to eq(0)
+      end
+
+      it "does not update lettings logs with ppcodenk nil" do
+        lettings_log.update!(ppcodenk: nil)
+        task.invoke
+        expect(lettings_log.reload.ppcodenk).to eq(nil)
+      end
+
+      context "with multiple lettings logs" do
+        let(:lettings_log_2) { create(:lettings_log, :completed) }
+        let(:lettings_log_3) { create(:lettings_log, :completed) }
+
+        it "only updates each log once" do
+          lettings_log.update!(ppcodenk: nil)
+          lettings_log_2.update!(ppcodenk: 0)
+          lettings_log_3.update!(ppcodenk: 1)
+          task.invoke
+          expect(lettings_log.reload.ppcodenk).to eq(nil)
+          expect(lettings_log_2.reload.ppcodenk).to eq(1)
+          expect(lettings_log_3.reload.ppcodenk).to eq(0)
+        end
+      end
+
+      it "does not update updated_at value" do
+        lettings_log.updated_at = Time.zone.local(2021, 3, 3)
+        lettings_log.save!(validate: false)
+        expect(lettings_log.updated_at.to_date).to eq(Time.zone.local(2021, 3, 3))
+        task.invoke
+        expect(lettings_log.updated_at.to_date).to eq(Time.zone.local(2021, 3, 3))
+      end
+
+      it "skips validations for previous years" do
+        lettings_log.update!(ppcodenk: 1)
+        lettings_log.startdate = Time.zone.local(2021, 3, 3)
+        lettings_log.save!(validate: false)
+        task.invoke
+        expect(lettings_log.reload.ppcodenk).to eq(0)
+      end
+    end
+  end
+end