diff --git a/api/v3/Contribution.php b/api/v3/Contribution.php
index 6396535fb355..02dae0513ddb 100644
--- a/api/v3/Contribution.php
+++ b/api/v3/Contribution.php
@@ -500,7 +500,40 @@ function civicrm_api3_contribution_completetransaction($params) {
     throw new API_Exception('failed to load related objects');
   }
 
-  return _ipn_process_transaction($params, $contribution, $input, $ids);
+  // @todo Copied from _ipn_process_transaction - needs cleanup/refactor
+  $objects = $contribution->_relatedObjects;
+  $objects['contribution'] = &$contribution;
+  $input['component'] = $contribution->_component;
+  $input['is_test'] = $contribution->is_test;
+  $input['amount'] = empty($input['total_amount']) ? $contribution->total_amount : $input['total_amount'];
+
+  if (isset($params['is_email_receipt'])) {
+    $input['is_email_receipt'] = $params['is_email_receipt'];
+  }
+  if (!empty($params['trxn_date'])) {
+    $input['trxn_date'] = $params['trxn_date'];
+  }
+  if (!empty($params['receive_date'])) {
+    $input['receive_date'] = $params['receive_date'];
+  }
+  if (empty($contribution->contribution_page_id)) {
+    static $domainFromName;
+    static $domainFromEmail;
+    if (empty($domainFromEmail) && (empty($params['receipt_from_name']) || empty($params['receipt_from_email']))) {
+      [$domainFromName, $domainFromEmail] = CRM_Core_BAO_Domain::getNameAndEmail(TRUE);
+    }
+    $input['receipt_from_name'] = CRM_Utils_Array::value('receipt_from_name', $params, $domainFromName);
+    $input['receipt_from_email'] = CRM_Utils_Array::value('receipt_from_email', $params, $domainFromEmail);
+  }
+  $input['card_type_id'] = $params['card_type_id'] ?? NULL;
+  $input['pan_truncation'] = $params['pan_truncation'] ?? NULL;
+  if (!empty($params['payment_instrument_id'])) {
+    $input['payment_instrument_id'] = $params['payment_instrument_id'];
+  }
+  return CRM_Contribute_BAO_Contribution::completeOrder($input,
+    !empty($objects['contributionRecur']) ? $objects['contributionRecur']->id : NULL,
+    $objects['contribution']->id ?? NULL,
+    $params['is_post_payment_create'] ?? NULL);
 }
 
 /**
@@ -632,7 +665,40 @@ function civicrm_api3_contribution_repeattransaction($params) {
   unset($contribution->id, $contribution->receive_date, $contribution->invoice_id);
   $contribution->receive_date = $params['receive_date'];
 
-  return _ipn_process_transaction($params, $contribution, $input, $ids);
+  // @todo Copied from _ipn_process_transaction - needs cleanup/refactor
+  $objects = $contribution->_relatedObjects;
+  $objects['contribution'] = &$contribution;
+  $input['component'] = $contribution->_component;
+  $input['is_test'] = $contribution->is_test;
+  $input['amount'] = empty($input['total_amount']) ? $contribution->total_amount : $input['total_amount'];
+
+  if (isset($params['is_email_receipt'])) {
+    $input['is_email_receipt'] = $params['is_email_receipt'];
+  }
+  if (!empty($params['trxn_date'])) {
+    $input['trxn_date'] = $params['trxn_date'];
+  }
+  if (!empty($params['receive_date'])) {
+    $input['receive_date'] = $params['receive_date'];
+  }
+  if (empty($contribution->contribution_page_id)) {
+    static $domainFromName;
+    static $domainFromEmail;
+    if (empty($domainFromEmail) && (empty($params['receipt_from_name']) || empty($params['receipt_from_email']))) {
+      [$domainFromName, $domainFromEmail] = CRM_Core_BAO_Domain::getNameAndEmail(TRUE);
+    }
+    $input['receipt_from_name'] = CRM_Utils_Array::value('receipt_from_name', $params, $domainFromName);
+    $input['receipt_from_email'] = CRM_Utils_Array::value('receipt_from_email', $params, $domainFromEmail);
+  }
+  $input['card_type_id'] = $params['card_type_id'] ?? NULL;
+  $input['pan_truncation'] = $params['pan_truncation'] ?? NULL;
+  if (!empty($params['payment_instrument_id'])) {
+    $input['payment_instrument_id'] = $params['payment_instrument_id'];
+  }
+  return CRM_Contribute_BAO_Contribution::completeOrder($input,
+    !empty($objects['contributionRecur']) ? $objects['contributionRecur']->id : NULL,
+    $objects['contribution']->id ?? NULL,
+    $params['is_post_payment_create'] ?? NULL);
 }
 
 /**
@@ -641,6 +707,8 @@ function civicrm_api3_contribution_repeattransaction($params) {
  * The IPN function is overloaded with two purposes - this is simply a wrapper for that
  * when separating them in the api layer.
  *
+ * @deprecated
+ *
  * @param array $params
  * @param CRM_Contribute_BAO_Contribution $contribution
  * @param array $input
@@ -652,6 +720,7 @@ function civicrm_api3_contribution_repeattransaction($params) {
  * @throws \CiviCRM_API3_Exception
  */
 function _ipn_process_transaction($params, $contribution, $input, $ids) {
+  CRM_Core_Error::deprecatedFunctionWarning('API3 contribution.completetransaction or contribution.repeattransaction');
   $objects = $contribution->_relatedObjects;
   $objects['contribution'] = &$contribution;
   $input['component'] = $contribution->_component;