diff --git a/app/code/Magento/Sales/Api/Data/OrderInterface.php b/app/code/Magento/Sales/Api/Data/OrderInterface.php
index 3ca936afd4090..b45fddc7d7354 100644
--- a/app/code/Magento/Sales/Api/Data/OrderInterface.php
+++ b/app/code/Magento/Sales/Api/Data/OrderInterface.php
@@ -581,6 +581,8 @@ public function getAdjustmentPositive();
     /**
      * Gets the applied rule IDs for the order.
      *
+     * Rules are comma separated if there are more than one.
+     *
      * @return string|null Applied rule IDs.
      */
     public function getAppliedRuleIds();
diff --git a/app/code/Magento/Sales/Api/Data/OrderItemInterface.php b/app/code/Magento/Sales/Api/Data/OrderItemInterface.php
index ae4064c0ab3d1..2aee648ef7c9f 100644
--- a/app/code/Magento/Sales/Api/Data/OrderItemInterface.php
+++ b/app/code/Magento/Sales/Api/Data/OrderItemInterface.php
@@ -415,6 +415,8 @@ public function getAmountRefunded();
     /**
      * Gets the applied rule IDs for the order item.
      *
+     * Rules are comma separated if there are more than one.
+     *
      * @return string|null Applied rule IDs.
      */
     public function getAppliedRuleIds();
diff --git a/app/code/Magento/Sales/Model/Order.php b/app/code/Magento/Sales/Model/Order.php
index 9f30342ed331f..ccf8b4470d942 100644
--- a/app/code/Magento/Sales/Model/Order.php
+++ b/app/code/Magento/Sales/Model/Order.php
@@ -2113,6 +2113,8 @@ public function getAdjustmentPositive()
     /**
      * Returns applied_rule_ids
      *
+     * Rules are comma separated if there are more than one.
+     *
      * @return string|null
      */
     public function getAppliedRuleIds()
diff --git a/app/code/Magento/Sales/Model/Order/Item.php b/app/code/Magento/Sales/Model/Order/Item.php
index d2f5f5ce56692..834d1e4694cf9 100644
--- a/app/code/Magento/Sales/Model/Order/Item.php
+++ b/app/code/Magento/Sales/Model/Order/Item.php
@@ -725,6 +725,8 @@ public function getAmountRefunded()
     /**
      * Returns applied_rule_ids
      *
+     * Rules are comma separated if there are more than one.
+     *
      * @return string|null
      */
     public function getAppliedRuleIds()