diff --git a/CRM/Contribute/BAO/Contribution.php b/CRM/Contribute/BAO/Contribution.php
index 9440b936b0bb..c7a653d6a0dc 100644
--- a/CRM/Contribute/BAO/Contribution.php
+++ b/CRM/Contribute/BAO/Contribution.php
@@ -4477,6 +4477,92 @@ public static function isSingleLineItem($id) {
     return ($lineItemCount == 1);
   }
 
+  /**
+   * Function to process additional payment for partial and refund contributions.
+   *
+   * This function is called via API payment.create function. All forms that add payments
+   * should use this.
+   *
+   * @param array $params
+   *   - contribution_id
+   *   - total_amount
+   *   - line_item
+   * @return \CRM_Financial_DAO_FinancialTrxn
+   *
+   * @throws \API_Exception
+   * @throws \CRM_Core_Exception
+   */
+  public static function addPayment($params) {
+    $contribution = civicrm_api3('Contribution', 'getsingle', ['id' => $params['contribution_id']]);
+    $contributionStatus = CRM_Contribute_PseudoConstant::contributionStatus($contribution['contribution_status_id'], 'name');
+    if ($contributionStatus != 'Partially paid'
+      && !($contributionStatus == 'Pending' && $contribution['is_pay_later'] == TRUE)
+    ) {
+      throw new API_Exception('Please select a contribution which has a partial or pending payment');
+    }
+    else {
+      // Check if pending contribution
+      $fullyPaidPayLater = FALSE;
+      if ($contributionStatus == 'Pending') {
+        $cmp = bccomp($contribution['total_amount'], $params['total_amount'], 5);
+        // Total payment amount is the whole amount paid against pending contribution
+        if ($cmp == 0 || $cmp == -1) {
+          civicrm_api3('Contribution', 'completetransaction', ['id' => $contribution['id']]);
+          // Get the trxn
+          $trxnId = CRM_Core_BAO_FinancialTrxn::getFinancialTrxnId($contribution['id'], 'DESC');
+          $ftParams = ['id' => $trxnId['financialTrxnId']];
+          $trxn = CRM_Core_BAO_FinancialTrxn::retrieve($ftParams, CRM_Core_DAO::$_nullArray);
+          $fullyPaidPayLater = TRUE;
+        }
+        else {
+          civicrm_api3('Contribution', 'create',
+            [
+              'id' => $contribution['id'],
+              'contribution_status_id' => 'Partially paid',
+            ]
+          );
+        }
+      }
+      if (!$fullyPaidPayLater) {
+        $trxn = CRM_Core_BAO_FinancialTrxn::getPartialPaymentTrxn($contribution, $params);
+        if (CRM_Utils_Array::value('line_item', $params) && !empty($trxn)) {
+          foreach ($params['line_item'] as $values) {
+            foreach ($values as $id => $amount) {
+              $p = ['id' => $id];
+              $check = CRM_Price_BAO_LineItem::retrieve($p, $defaults);
+              if (empty($check)) {
+                throw new API_Exception('Please specify a valid Line Item.');
+              }
+              // get financial item
+              $sql = "SELECT fi.id
+              FROM civicrm_financial_item fi
+              INNER JOIN civicrm_line_item li ON li.id = fi.entity_id and fi.entity_table = 'civicrm_line_item'
+              WHERE li.contribution_id = %1 AND li.id = %2";
+              $sqlParams = [
+                1 => [$params['contribution_id'], 'Integer'],
+                2 => [$id, 'Integer'],
+              ];
+              $fid = CRM_Core_DAO::singleValueQuery($sql, $sqlParams);
+              // Record Entity Financial Trxn
+              $eftParams = [
+                'entity_table' => 'civicrm_financial_item',
+                'financial_trxn_id' => $trxn->id,
+                'amount' => $amount,
+                'entity_id' => $fid,
+              ];
+              civicrm_api3('EntityFinancialTrxn', 'create', $eftParams);
+            }
+          }
+        }
+        elseif (!empty($trxn)) {
+          CRM_Contribute_BAO_Contribution::assignProportionalLineItems($params, $trxn->id, $contribution['total_amount']);
+        }
+      }
+    }
+    return $trxn;
+
+  }
+
   /**
    * Complete an order.
    *
diff --git a/api/v3/Payment.php b/api/v3/Payment.php
index 1c144b43bc07..b80e899aa6ca 100644
--- a/api/v3/Payment.php
+++ b/api/v3/Payment.php
@@ -132,74 +132,8 @@ function civicrm_api3_payment_create(&$params) {
     civicrm_api3('Payment', 'cancel', $params);
     $params['total_amount'] = $amount;
   }
-  // Get contribution
-  $contribution = civicrm_api3('Contribution', 'getsingle', array('id' => $params['contribution_id']));
-  $contributionStatus = CRM_Contribute_PseudoConstant::contributionStatus($contribution['contribution_status_id'], 'name');
-  if ($contributionStatus != 'Partially paid'
-    && !($contributionStatus == 'Pending' && $contribution['is_pay_later'] == TRUE)
-  ) {
-    throw new API_Exception('Please select a contribution which has a partial or pending payment');
-  }
-  else {
-    // Check if pending contribution
-    $fullyPaidPayLater = FALSE;
-    if ($contributionStatus == 'Pending') {
-      $cmp = bccomp($contribution['total_amount'], $params['total_amount'], 5);
-      // Total payment amount is the whole amount paid against pending contribution
-      if ($cmp == 0 || $cmp == -1) {
-        civicrm_api3('Contribution', 'completetransaction', array('id' => $contribution['id']));
-        // Get the trxn
-        $trxnId = CRM_Core_BAO_FinancialTrxn::getFinancialTrxnId($contribution['id'], 'DESC');
-        $ftParams = array('id' => $trxnId['financialTrxnId']);
-        $trxn = CRM_Core_BAO_FinancialTrxn::retrieve($ftParams, CRM_Core_DAO::$_nullArray);
-        $fullyPaidPayLater = TRUE;
-      }
-      else {
-        civicrm_api3('Contribution', 'create',
-          array(
-            'id' => $contribution['id'],
-            'contribution_status_id' => 'Partially paid',
-          )
-        );
-      }
-    }
-    if (!$fullyPaidPayLater) {
-      $trxn = CRM_Core_BAO_FinancialTrxn::getPartialPaymentTrxn($contribution, $params);
-      if (CRM_Utils_Array::value('line_item', $params) && !empty($trxn)) {
-        foreach ($params['line_item'] as $values) {
-          foreach ($values as $id => $amount) {
-            $p = array('id' => $id);
-            $check = CRM_Price_BAO_LineItem::retrieve($p, $defaults);
-            if (empty($check)) {
-              throw new API_Exception('Please specify a valid Line Item.');
-            }
-            // get financial item
-            $sql = "SELECT fi.id
-              FROM civicrm_financial_item fi
-              INNER JOIN civicrm_line_item li ON li.id = fi.entity_id and fi.entity_table = 'civicrm_line_item'
-              WHERE li.contribution_id = %1 AND li.id = %2";
-            $sqlParams = array(
-              1 => array($params['contribution_id'], 'Integer'),
-              2 => array($id, 'Integer'),
-            );
-            $fid = CRM_Core_DAO::singleValueQuery($sql, $sqlParams);
-            // Record Entity Financial Trxn
-            $eftParams = array(
-              'entity_table' => 'civicrm_financial_item',
-              'financial_trxn_id' => $trxn->id,
-              'amount' => $amount,
-              'entity_id' => $fid,
-            );
-            civicrm_api3('EntityFinancialTrxn', 'create', $eftParams);
-          }
-        }
-      }
-      elseif (!empty($trxn)) {
-        // Assign the lineitems proportionally
-        CRM_Contribute_BAO_Contribution::assignProportionalLineItems($params, $trxn->id, $contribution['total_amount']);
-      }
-    }
-  }
+  $trxn = CRM_Contribute_BAO_Contribution::addPayment($params);
+
   $values = array();
   _civicrm_api3_object_to_array_unique_fields($trxn, $values[$trxn->id]);
   return civicrm_api3_create_success($values, $params, 'Payment', 'create', $trxn);