diff --git a/CRM/Event/Form/Participant.php b/CRM/Event/Form/Participant.php
index fee7ae3faaa4..885b98b75f98 100644
--- a/CRM/Event/Form/Participant.php
+++ b/CRM/Event/Form/Participant.php
@@ -524,8 +524,8 @@ public function setDefaultValues(): array {
 
       $this->_eventTypeId = CRM_Core_DAO::getFieldValue('CRM_Event_DAO_Event', $eventID, 'event_type_id', 'id');
 
-      $this->_discountId = CRM_Core_DAO::getFieldValue('CRM_Event_DAO_Participant', $this->_id, 'discount_id');
-      if ($this->_discountId) {
+      if ($this->getDiscountID()) {
+        // This doesn't seem used....
         $this->set('discountId', $this->_discountId);
       }
     }
@@ -1436,8 +1436,8 @@ public function buildEventFeeForm($form) {
 
       //retrieve custom information
       $form->_values = [];
-      CRM_Event_Form_Registration::initEventFee($form, $event['id'], FALSE);
-      CRM_Event_Form_Registration_Register::buildAmount($form, TRUE, $form->_discountId);
+      CRM_Event_Form_Registration::initEventFee($form, $event['id'], FALSE, $form->getDiscountID());
+      CRM_Event_Form_Registration_Register::buildAmount($form, TRUE, $form->getDiscountID());
       $lineItem = [];
       $totalTaxAmount = 0;
       if (!CRM_Utils_System::isNull($form->_values['line_items'] ?? NULL)) {
@@ -2266,4 +2266,28 @@ protected function sendReceipts($params, $total_amount, array $customFields, arr
     return ['sent' => count($sent), 'not_sent' => count($notSent)];
   }
 
+  /**
+   * Get the discount ID.
+   *
+   * @return int|null
+   *
+   * @api This function will not change in a minor release and is supported for
+   * use outside of core. This annotation / external support for properties
+   * is only given where there is specific test cover.
+   *
+   * @noinspection PhpDocMissingThrowsInspection
+   * @noinspection PhpUnhandledExceptionInspection
+   */
+  public function getDiscountID(): ?int {
+    if ($this->_discountId === NULL) {
+      if ($this->getParticipantID()) {
+        $this->_discountId = (int) CRM_Core_DAO::getFieldValue('CRM_Event_DAO_Participant', $this->getParticipantID(), 'discount_id');
+      }
+      else {
+        CRM_Core_BAO_Discount::findSet($this->getEventID(), 'civicrm_event');
+      }
+    }
+    return $this->_discountId ?: NULL;
+  }
+
 }
diff --git a/CRM/Event/Form/ParticipantFeeSelection.php b/CRM/Event/Form/ParticipantFeeSelection.php
index c42cdc721ffe..e27662096af5 100644
--- a/CRM/Event/Form/ParticipantFeeSelection.php
+++ b/CRM/Event/Form/ParticipantFeeSelection.php
@@ -172,7 +172,7 @@ public function buildQuickForm() {
     //retrieve custom information
     $this->_values = [];
 
-    CRM_Event_Form_Registration::initEventFee($this, $event['id'], $this->_action !== CRM_Core_Action::UPDATE);
+    CRM_Event_Form_Registration::initEventFee($this, $event['id'], $this->_action !== CRM_Core_Action::UPDATE, $this->getDiscountID());
     CRM_Event_Form_Registration_Register::buildAmount($this, TRUE);
 
     if (!CRM_Utils_System::isNull($this->_values['line_items'] ?? NULL)) {
@@ -225,6 +225,23 @@ public function buildQuickForm() {
     $this->addFormRule(['CRM_Event_Form_ParticipantFeeSelection', 'formRule'], $this);
   }
 
+  /**
+   * Get the discount ID.
+   *
+   * @return int|null
+   *
+   * @api This function will not change in a minor release and is supported for
+   * use outside of core. This annotation / external support for properties
+   * is only given where there is specific test cover.
+   *
+   * @noinspection PhpDocMissingThrowsInspection
+   * @noinspection PhpUnhandledExceptionInspection
+   */
+  public function getDiscountID(): ?int {
+    $discountID = (int) CRM_Core_BAO_Discount::findSet($this->getEventID(), 'civicrm_event');
+    return $discountID ?: NULL;
+  }
+
   /**
    * @param $fields
    * @param $files
@@ -390,4 +407,23 @@ private function emailReceipt(array $params): void {
     CRM_Core_BAO_MessageTemplate::sendTemplate($sendTemplateParams);
   }
 
+  /**
+   * Get the event ID.
+   *
+   * This function is supported for use outside of core.
+   *
+   * @api This function will not change in a minor release and is supported for
+   * use outside of core. This annotation / external support for properties
+   * is only given where there is specific test cover.
+   *
+   * @return int
+   * @throws \CRM_Core_Exception
+   */
+  public function getEventID(): int {
+    if (!$this->_eventId) {
+      $this->_eventId = CRM_Core_DAO::getFieldValue('CRM_Event_DAO_Participant', $this->_participantId, 'event_id');
+    }
+    return $this->_eventId;
+  }
+
 }
diff --git a/CRM/Event/Form/Registration.php b/CRM/Event/Form/Registration.php
index ebde060eb3b3..5685a1d682d6 100644
--- a/CRM/Event/Form/Registration.php
+++ b/CRM/Event/Form/Registration.php
@@ -297,8 +297,9 @@ public function preProcess() {
         ));
         $this->assignPaymentProcessor($isPayLater);
       }
-      //init event fee.
-      self::initEventFee($this, $this->_eventId);
+
+      $discountId = $this->getDiscountID();
+      self::initEventFee($this, $this->_eventId, TRUE, $discountId);
 
       // get the profile ids
       $ufJoinParams = [
@@ -570,18 +571,15 @@ public function buildCustom($id, $name) {
    * @param int $eventID
    * @param bool $doNotIncludeExpiredFields
    *   See CRM-16456.
+   * @param int|null $discountId
+   *   ID of any discount in use.
    *
    * @throws Exception
    */
-  public static function initEventFee(&$form, $eventID, $doNotIncludeExpiredFields = TRUE) {
+  public static function initEventFee(&$form, $eventID, $doNotIncludeExpiredFields = TRUE, $discountId = NULL) {
     // get price info
 
     // retrive all active price set fields.
-    $discountId = CRM_Core_BAO_Discount::findSet($eventID, 'civicrm_event');
-    if (property_exists($form, '_discountId') && $form->_discountId) {
-      $discountId = $form->_discountId;
-    }
-
     if ($discountId) {
       $priceSetId = CRM_Core_DAO::getFieldValue('CRM_Core_BAO_Discount', $discountId, 'price_set_id');
     }
@@ -892,7 +890,7 @@ protected function addParticipant(&$form, $contactID) {
     $participantParams['custom'] = [];
     foreach ($form->_params as $paramName => $paramValue) {
       if (strpos($paramName, 'custom_') === 0) {
-        list($customFieldID, $customValueID) = CRM_Core_BAO_CustomField::getKeyID($paramName, TRUE);
+        [$customFieldID, $customValueID] = CRM_Core_BAO_CustomField::getKeyID($paramName, TRUE);
         CRM_Core_BAO_CustomField::formatCustomField($customFieldID, $participantParams['custom'], $paramValue, 'Participant', $customValueID);
 
       }
@@ -1717,4 +1715,21 @@ private function getInfoPageUrl(): string {
     );
   }
 
+  /**
+   * Get the discount ID.
+   *
+   * @return int|null
+   *
+   * @api This function will not change in a minor release and is supported for
+   * use outside of core. This annotation / external support for properties
+   * is only given where there is specific test cover.
+   *
+   * @noinspection PhpUnhandledExceptionInspection
+   * @noinspection PhpDocMissingThrowsInspection
+   */
+  protected function getDiscountID(): ?int {
+    $id = CRM_Core_BAO_Discount::findSet($this->getEventID(), 'civicrm_event');
+    return $id ?: NULL;
+  }
+
 }