diff --git a/app/models/legacy_user.rb b/app/models/legacy_user.rb
new file mode 100644
index 000000000..dcab274a6
--- /dev/null
+++ b/app/models/legacy_user.rb
@@ -0,0 +1,5 @@
+class LegacyUser < ApplicationRecord
+  belongs_to :user
+
+  validates :old_user_id, uniqueness: true
+end
diff --git a/app/models/user.rb b/app/models/user.rb
index 56dd2821f..707a8e41c 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -11,6 +11,7 @@ class User < ApplicationRecord
   has_many :managed_lettings_logs, through: :organisation
   has_many :owned_sales_logs, through: :organisation
   has_many :managed_sales_logs, through: :organisation
+  has_many :legacy_users
 
   validates :name, presence: true
   validates :email, presence: true
@@ -113,7 +114,11 @@ class User < ApplicationRecord
   end
 
   def was_migrated_from_softwire?
-    old_user_id.present?
+    legacy_users.any?
+  end
+
+  def old_user_id
+    legacy_users&.first&.old_user_id || read_attribute(:old_user_id)
   end
 
   def send_confirmation_instructions
diff --git a/app/services/imports/lettings_logs_import_service.rb b/app/services/imports/lettings_logs_import_service.rb
index 97be11dc2..e9d44a87c 100644
--- a/app/services/imports/lettings_logs_import_service.rb
+++ b/app/services/imports/lettings_logs_import_service.rb
@@ -226,7 +226,7 @@ module Imports
       # Sets the log creator
       owner_id = field_value(xml_doc, "meta", "owner-user-id").strip
       if owner_id.present?
-        attributes["created_by"] = User.find_by(old_user_id: owner_id)
+        attributes["created_by"] = LegacyUser.find_by(old_user_id: owner_id)&.user
       end
 
       apply_date_consistency!(attributes)
diff --git a/app/services/imports/user_import_service.rb b/app/services/imports/user_import_service.rb
index 1d1fbc84e..f5a730479 100644
--- a/app/services/imports/user_import_service.rb
+++ b/app/services/imports/user_import_service.rb
@@ -17,7 +17,7 @@ module Imports
       name = user_field_value(xml_document, "full-name") || email
       deleted = user_field_value(xml_document, "deleted")
 
-      if User.find_by(old_user_id:, organisation:)
+      if LegacyUser.find_by(old_user_id:)
         @logger.warn("User #{name} with old user id #{old_user_id} is already present, skipping.")
       elsif deleted == "true"
         @logger.warn("User #{name} with old user id #{old_user_id} is deleted, skipping.")
@@ -25,20 +25,22 @@ module Imports
         is_dpo = user.is_data_protection_officer? || is_dpo?(user_field_value(xml_document, "user-type"))
         role = highest_role(user.role, role(user_field_value(xml_document, "user-type")))
         user.update!(role:, is_dpo:)
+        user.legacy_users.create!(old_user_id:)
         @logger.info("Found duplicated email, updating user #{user.id} with role #{role} and is_dpo #{is_dpo}")
       else
-        User.create!(
+        user = User.create!(
           email:,
           name:,
           password: Devise.friendly_token,
           phone: user_field_value(xml_document, "telephone-no"),
-          old_user_id:,
           organisation:,
           role: role(user_field_value(xml_document, "user-type")),
           is_dpo: is_dpo?(user_field_value(xml_document, "user-type")),
           is_key_contact: is_key_contact?(user_field_value(xml_document, "contact-priority-id")),
           active: user_field_value(xml_document, "active"),
         )
+        user.legacy_users.create!(old_user_id:)
+        user
       end
     end
 
diff --git a/db/migrate/20220923093628_create_legacy_users.rb b/db/migrate/20220923093628_create_legacy_users.rb
new file mode 100644
index 000000000..a8f92545d
--- /dev/null
+++ b/db/migrate/20220923093628_create_legacy_users.rb
@@ -0,0 +1,12 @@
+class CreateLegacyUsers < ActiveRecord::Migration[7.0]
+  def change
+    create_table :legacy_users do |t|
+      t.string :old_user_id
+      t.integer :user_id
+
+      t.timestamps
+    end
+
+    add_index :legacy_users, :old_user_id, unique: true
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 87714f00f..0af743586 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_09_20_132907) do
+ActiveRecord::Schema[7.0].define(version: 2022_09_23_093628) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
@@ -42,6 +42,14 @@ ActiveRecord::Schema[7.0].define(version: 2022_09_20_132907) do
     t.index ["start_year", "lettype", "beds", "la"], name: "index_la_rent_ranges_on_start_year_and_lettype_and_beds_and_la", unique: true
   end
 
+  create_table "legacy_users", force: :cascade do |t|
+    t.string "old_user_id"
+    t.integer "user_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["old_user_id"], name: "index_legacy_users_on_old_user_id", unique: true
+  end
+
   create_table "lettings_logs", force: :cascade do |t|
     t.integer "status", default: 0
     t.datetime "created_at", null: false
@@ -232,12 +240,12 @@ ActiveRecord::Schema[7.0].define(version: 2022_09_20_132907) do
     t.integer "void_date_value_check"
     t.integer "housingneeds_type"
     t.integer "housingneeds_other"
-    t.index ["created_by_id"], name: "index_lettings_logs_on_created_by_id"
-    t.index ["location_id"], name: "index_lettings_logs_on_location_id"
-    t.index ["managing_organisation_id"], name: "index_lettings_logs_on_managing_organisation_id"
-    t.index ["old_id"], name: "index_lettings_logs_on_old_id", unique: true
-    t.index ["owning_organisation_id"], name: "index_lettings_logs_on_owning_organisation_id"
-    t.index ["scheme_id"], name: "index_lettings_logs_on_scheme_id"
+    t.index ["created_by_id"], name: "index_case_logs_on_created_by_id"
+    t.index ["location_id"], name: "index_case_logs_on_location_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
+    t.index ["owning_organisation_id"], name: "index_case_logs_on_owning_organisation_id"
+    t.index ["scheme_id"], name: "index_case_logs_on_scheme_id"
   end
 
   create_table "locations", force: :cascade do |t|
diff --git a/spec/factories/legacy_user.rb b/spec/factories/legacy_user.rb
new file mode 100644
index 000000000..b1f5578d9
--- /dev/null
+++ b/spec/factories/legacy_user.rb
@@ -0,0 +1,6 @@
+FactoryBot.define do
+  factory :legacy_user do
+    old_user_id { }
+    user
+  end
+end
diff --git a/spec/factories/user.rb b/spec/factories/user.rb
index e021e0727..ce286f8e7 100644
--- a/spec/factories/user.rb
+++ b/spec/factories/user.rb
@@ -5,7 +5,6 @@ FactoryBot.define do
     password { "pAssword1" }
     organisation
     role { "data_provider" }
-    old_user_id { 2 }
     trait :data_coordinator do
       role { "data_coordinator" }
     end
@@ -19,5 +18,15 @@ FactoryBot.define do
     confirmed_at { Time.zone.now }
     created_at { Time.zone.now }
     updated_at { Time.zone.now }
+
+    transient do
+      old_user_id { SecureRandom.uuid }
+    end
+
+    after(:create) do |user, evaulator|
+      FactoryBot.create(:legacy_user, old_user_id: evaulator.old_user_id, user:)
+
+      user.reload
+    end
   end
 end
diff --git a/spec/models/user_spec.rb b/spec/models/user_spec.rb
index ed77046fd..bad70e31e 100644
--- a/spec/models/user_spec.rb
+++ b/spec/models/user_spec.rb
@@ -2,7 +2,7 @@ require "rails_helper"
 
 RSpec.describe User, type: :model do
   describe "#new" do
-    let(:user) { FactoryBot.create(:user) }
+    let(:user) { FactoryBot.create(:user, old_user_id: "3") }
     let(:other_organisation) { FactoryBot.create(:organisation) }
     let!(:owned_lettings_log) do
       FactoryBot.create(
@@ -74,6 +74,14 @@ RSpec.describe User, type: :model do
       expect(user.need_two_factor_authentication?(nil)).to be false
     end
 
+    it "can have one or more legacy users" do
+      expect(user.old_user_id).to eq("3")
+
+      user.legacy_users.destroy_all
+      user.update!(old_user_id: "2")
+      expect(user.old_user_id).to eq("2")
+    end
+
     it "is confirmable" do
       allow(DeviseNotifyMailer).to receive(:confirmation_instructions).and_return(OpenStruct.new(deliver: true))
       expect(DeviseNotifyMailer).to receive(:confirmation_instructions).once
diff --git a/spec/requests/users_controller_spec.rb b/spec/requests/users_controller_spec.rb
index 3168defa1..a404bbd97 100644
--- a/spec/requests/users_controller_spec.rb
+++ b/spec/requests/users_controller_spec.rb
@@ -1381,7 +1381,7 @@ RSpec.describe UsersController, type: :request do
           end
 
           before do
-            user.update(old_user_id: nil)
+            user.legacy_users.destroy_all
           end
 
           it "allows changing email and dpo" do
diff --git a/spec/services/imports/user_import_service_spec.rb b/spec/services/imports/user_import_service_spec.rb
index c4aea00bc..1257679ff 100644
--- a/spec/services/imports/user_import_service_spec.rb
+++ b/spec/services/imports/user_import_service_spec.rb
@@ -32,7 +32,7 @@ RSpec.describe Imports::UserImportService do
       FactoryBot.create(:organisation, old_org_id:)
       import_service.create_users("user_directory")
 
-      user = User.find_by(old_user_id:)
+      user = LegacyUser.find_by(old_user_id:)&.user
       expect(user.name).to eq("John Doe")
       expect(user.email).to eq("john.doe@gov.uk")
       expect(user.encrypted_password).not_to be_nil
@@ -54,7 +54,8 @@ RSpec.describe Imports::UserImportService do
       it "sets their role correctly" do
         FactoryBot.create(:organisation, old_org_id:)
         import_service.create_users("user_directory")
-        expect(User.find_by(old_user_id:)).to be_data_coordinator
+        user = LegacyUser.find_by(old_user_id:)&.user
+        expect(user).to be_data_coordinator
       end
     end
 
@@ -65,7 +66,7 @@ RSpec.describe Imports::UserImportService do
         FactoryBot.create(:organisation, old_org_id:)
         import_service.create_users("user_directory")
 
-        user = User.find_by(old_user_id:)
+        user = LegacyUser.find_by(old_user_id:)&.user
         expect(user.is_data_protection_officer?).to be true
       end
     end
@@ -77,7 +78,7 @@ RSpec.describe Imports::UserImportService do
         FactoryBot.create(:organisation, old_org_id:)
         import_service.create_users("user_directory")
 
-        user = User.find_by(old_user_id:)
+        user = LegacyUser.find_by(old_user_id: )&.user
         expect(user.is_key_contact?).to be true
       end
     end
@@ -89,7 +90,7 @@ RSpec.describe Imports::UserImportService do
         FactoryBot.create(:organisation, old_org_id:)
         import_service.create_users("user_directory")
 
-        user = User.find_by(old_user_id:)
+        user = LegacyUser.find_by(old_user_id:)&.user
         expect(user.is_key_contact?).to be true
       end
     end
@@ -118,10 +119,19 @@ RSpec.describe Imports::UserImportService do
           expect(user.reload).to be_data_coordinator
         end
 
-        it "does not create a new record" do
+        it "does not create a new user record" do
           expect { import_service.create_users("user_directory") }
             .not_to change(User, :count)
         end
+
+        it "creates a new legacy user record" do
+          expect { import_service.create_users("user_directory") }.to change(LegacyUser, :count)
+        end
+
+        it "associates the legacy user with the existing user" do
+          import_service.create_users("user_directory")
+          expect(LegacyUser.find_by(old_user_id:)&.user).to eq(user)
+        end
       end
 
       context "when the duplicate role is lower than the original role" do
@@ -159,7 +169,8 @@ RSpec.describe Imports::UserImportService do
 
         it "marks them as not active" do
           import_service.create_users("user_directory")
-          expect(User.find_by(old_user_id:).active).to be false
+          user = LegacyUser.find_by(old_user_id:)&.user
+          expect(user.active).to be false
         end
       end
     end