diff --git a/CHANGELOG b/CHANGELOG
index 0634a804b2a..d2582ceef7d 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -16,6 +16,7 @@
 * Decidir: Pass CVV for NT [almalee24] #5205
 * NMI: Add customer vault fields [yunnydang] #5215
 * CheckoutV2: Add inquire method [almalee24] #5209
+* SecurePayAU: Send order ID for payments with stored card [dacook] #3979
 
 == Version 1.137.0 (August 2, 2024)
 * Unlock dependency on `rexml` to allow fixing a CVE (#5181).
diff --git a/lib/active_merchant/billing/gateways/secure_pay_au.rb b/lib/active_merchant/billing/gateways/secure_pay_au.rb
index a23c6f65967..0e7de2a701f 100644
--- a/lib/active_merchant/billing/gateways/secure_pay_au.rb
+++ b/lib/active_merchant/billing/gateways/secure_pay_au.rb
@@ -207,6 +207,7 @@ def build_periodic_item(action, money, credit_card, options)
         end
         xml.tag! 'amount', amount(money)
         xml.tag! 'periodicType', PERIODIC_TYPES[action] if PERIODIC_TYPES[action]
+        xml.tag! 'transactionReference', options[:order_id] if options[:order_id]
 
         xml.target!
       end
diff --git a/test/remote/gateways/remote_secure_pay_au_test.rb b/test/remote/gateways/remote_secure_pay_au_test.rb
index 202b5f44e0c..41fefc26397 100644
--- a/test/remote/gateways/remote_secure_pay_au_test.rb
+++ b/test/remote/gateways/remote_secure_pay_au_test.rb
@@ -21,7 +21,7 @@ def setup
     @credit_card = credit_card('4242424242424242', { month: 9, year: 15 })
 
     @options = {
-      order_id: '2',
+      order_id: 'order123',
       billing_address: address,
       description: 'Store Purchase'
     }
@@ -166,6 +166,7 @@ def test_successful_triggered_payment
     assert response = @gateway.purchase(12300, 'test1234', @options)
     assert_success response
     assert_equal response.params['amount'], '12300'
+    assert_equal response.params['ponum'], 'order123'
 
     assert_equal 'Approved', response.message
   end
diff --git a/test/unit/gateways/secure_pay_au_test.rb b/test/unit/gateways/secure_pay_au_test.rb
index 4bbd0213712..88f9a83f32c 100644
--- a/test/unit/gateways/secure_pay_au_test.rb
+++ b/test/unit/gateways/secure_pay_au_test.rb
@@ -13,7 +13,7 @@ def setup
     @amount = 100
 
     @options = {
-      order_id: '1',
+      order_id: 'order123',
       billing_address: address,
       description: 'Store Purchase'
     }
@@ -79,6 +79,14 @@ def test_purchase_with_stored_id_calls_commit_periodic
     @gateway.purchase(@amount, '123', @options)
   end
 
+  def test_periodic_payment_submits_order_id
+    stub_comms(@gateway, :ssl_request) do
+      @gateway.purchase(@amount, '123', @options)
+    end.check_request do |method, endpoint, data, headers|
+      assert_match(/<transactionReference>order123<\/transactionReference>/, data)
+    end.respond_with(successful_purchase_response)
+  end
+
   def test_purchase_with_creditcard_calls_commit_with_purchase
     @gateway.expects(:commit).with(:purchase, anything)