diff --git a/CRM/Member/Form/MembershipRenewal.php b/CRM/Member/Form/MembershipRenewal.php
index 0d7e13eab208..a4dd83f0ac24 100644
--- a/CRM/Member/Form/MembershipRenewal.php
+++ b/CRM/Member/Form/MembershipRenewal.php
@@ -595,9 +595,8 @@ protected function submit() {
       $membershipSource = $this->_params['membership_source'];
     }
 
-    // @todo Move this into CRM_Member_BAO_Membership::processMembership
     $pending = ($this->_params['contribution_status_id'] == CRM_Core_PseudoConstant::getKey('CRM_Contribute_BAO_Contribution', 'contribution_status_id', 'Pending'));
-    list($membership) = CRM_Member_BAO_Membership::processMembership(
+    list($membership) = $this->processMembership(
       $this->_contactID, $this->_params['membership_type_id'][1], $isTestMembership,
       $renewalDate, NULL, $customFieldsFormatted, $numRenewTerms, $this->_membershipId,
       $pending,
@@ -735,4 +734,254 @@ protected function sendReceipt($membership) {
     );
   }
 
+  /**
+   * Process membership.
+   *
+   * This is duplicated from the BAO class - on the basis that it's actually easier to divide & conquer when
+   * it comes to clearing up really bad code.
+   *
+   * @param int $contactID
+   * @param int $membershipTypeID
+   * @param bool $is_test
+   * @param string $changeToday
+   * @param int $modifiedID
+   * @param $customFieldsFormatted
+   * @param $numRenewTerms
+   * @param int $membershipID
+   * @param $pending
+   * @param int $contributionRecurID
+   * @param $membershipSource
+   * @param $isPayLater
+   * @param int $campaignId
+   * @param array $formDates
+   * @param null|CRM_Contribute_BAO_Contribution $contribution
+   * @param array $lineItems
+   *
+   * @return array
+   * @throws \CRM_Core_Exception
+   * @throws \CiviCRM_API3_Exception
+   */
+  public function processMembership($contactID, $membershipTypeID, $is_test, $changeToday, $modifiedID, $customFieldsFormatted, $numRenewTerms, $membershipID, $pending, $contributionRecurID, $membershipSource, $isPayLater, $campaignId, $formDates = [], $contribution = NULL, $lineItems = []) {
+    $renewalMode = $updateStatusId = FALSE;
+    $allStatus = CRM_Member_PseudoConstant::membershipStatus();
+    $format = '%Y%m%d';
+    $statusFormat = '%Y-%m-%d';
+    $membershipTypeDetails = CRM_Member_BAO_MembershipType::getMembershipTypeDetails($membershipTypeID);
+    $dates = [];
+    $ids = [];
+
+    // CRM-7297 - allow membership type to be be changed during renewal so long as the parent org of new membershipType
+    // is the same as the parent org of an existing membership of the contact
+    $currentMembership = CRM_Member_BAO_Membership::getContactMembership($contactID, $membershipTypeID,
+      $is_test, $membershipID, TRUE
+    );
+    if ($currentMembership) {
+      $renewalMode = TRUE;
+
+      // Do NOT do anything.
+      //1. membership with status : PENDING/CANCELLED (CRM-2395)
+      //2. Paylater/IPN renew. CRM-4556.
+      if ($pending || in_array($currentMembership['status_id'], [
+        array_search('Pending', $allStatus),
+        // CRM-15475
+        array_search('Cancelled', CRM_Member_PseudoConstant::membershipStatus(NULL, " name = 'Cancelled' ", 'name', FALSE, TRUE)),
+      ])) {
+
+        $memParams = [
+          'id' => $currentMembership['id'],
+          'contribution' => $contribution,
+          'status_id' => $currentMembership['status_id'],
+          'start_date' => $currentMembership['start_date'],
+          'end_date' => $currentMembership['end_date'],
+          'line_item' => $lineItems,
+          'join_date' => $currentMembership['join_date'],
+          'membership_type_id' => $membershipTypeID,
+          'max_related' => !empty($membershipTypeDetails['max_related']) ? $membershipTypeDetails['max_related'] : NULL,
+          'membership_activity_status' => ($pending || $isPayLater) ? 'Scheduled' : 'Completed',
+        ];
+        if ($contributionRecurID) {
+          $memParams['contribution_recur_id'] = $contributionRecurID;
+        }
+        // @todo stop passing $ids - it is empty
+        $membership = CRM_Member_BAO_Membership::create($memParams, $ids);
+        return [$membership, $renewalMode, $dates];
+      }
+
+      // Check and fix the membership if it is STALE
+      CRM_Member_BAO_Membership::fixMembershipStatusBeforeRenew($currentMembership, $changeToday);
+
+      // Now Renew the membership
+      if (!$currentMembership['is_current_member']) {
+        // membership is not CURRENT
+
+        // CRM-7297 Membership Upsell - calculate dates based on new membership type
+        $dates = CRM_Member_BAO_MembershipType::getRenewalDatesForMembershipType($currentMembership['id'],
+          $changeToday,
+          $membershipTypeID,
+          $numRenewTerms
+        );
+
+        $currentMembership['join_date'] = CRM_Utils_Date::customFormat($currentMembership['join_date'], $format);
+        foreach (['start_date', 'end_date'] as $dateType) {
+          $currentMembership[$dateType] = $formDates[$dateType] ?? NULL;
+          if (empty($currentMembership[$dateType])) {
+            $currentMembership[$dateType] = $dates[$dateType] ?? NULL;
+          }
+        }
+        $currentMembership['is_test'] = $is_test;
+
+        if (!empty($membershipSource)) {
+          $currentMembership['source'] = $membershipSource;
+        }
+        else {
+          $currentMembership['source'] = CRM_Core_DAO::getFieldValue('CRM_Member_DAO_Membership',
+            $currentMembership['id'],
+            'source'
+          );
+        }
+
+        if (!empty($currentMembership['id'])) {
+          $ids['membership'] = $currentMembership['id'];
+        }
+        $memParams = $currentMembership;
+        $memParams['membership_type_id'] = $membershipTypeID;
+
+        //set the log start date.
+        $memParams['log_start_date'] = CRM_Utils_Date::customFormat($dates['log_start_date'], $format);
+      }
+      else {
+
+        // CURRENT Membership
+        $membership = new CRM_Member_DAO_Membership();
+        $membership->id = $currentMembership['id'];
+        $membership->find(TRUE);
+        // CRM-7297 Membership Upsell - calculate dates based on new membership type
+        $dates = CRM_Member_BAO_MembershipType::getRenewalDatesForMembershipType($membership->id,
+          $changeToday,
+          $membershipTypeID,
+          $numRenewTerms
+        );
+
+        // Insert renewed dates for CURRENT membership
+        $memParams = [];
+        $memParams['join_date'] = CRM_Utils_Date::isoToMysql($membership->join_date);
+        $memParams['start_date'] = CRM_Utils_Array::value('start_date', $formDates, CRM_Utils_Date::isoToMysql($membership->start_date));
+        $memParams['end_date'] = $formDates['end_date'] ?? NULL;
+        if (empty($memParams['end_date'])) {
+          $memParams['end_date'] = $dates['end_date'] ?? NULL;
+        }
+        $memParams['membership_type_id'] = $membershipTypeID;
+
+        //set the log start date.
+        $memParams['log_start_date'] = CRM_Utils_Date::customFormat($dates['log_start_date'], $format);
+
+        //CRM-18067
+        if (!empty($membershipSource)) {
+          $memParams['source'] = $membershipSource;
+        }
+        elseif (empty($membership->source)) {
+          $memParams['source'] = CRM_Core_DAO::getFieldValue('CRM_Member_DAO_Membership',
+            $currentMembership['id'],
+            'source'
+          );
+        }
+
+        if (!empty($currentMembership['id'])) {
+          $ids['membership'] = $currentMembership['id'];
+        }
+        $memParams['membership_activity_status'] = ($pending || $isPayLater) ? 'Scheduled' : 'Completed';
+      }
+      //CRM-4555
+      if ($pending) {
+        $updateStatusId = array_search('Pending', $allStatus);
+      }
+    }
+    else {
+      // NEW Membership
+      $memParams = [
+        'contact_id' => $contactID,
+        'membership_type_id' => $membershipTypeID,
+      ];
+
+      if (!$pending) {
+        $dates = CRM_Member_BAO_MembershipType::getDatesForMembershipType($membershipTypeID, NULL, NULL, NULL, $numRenewTerms);
+
+        foreach (['join_date', 'start_date', 'end_date'] as $dateType) {
+          $memParams[$dateType] = $formDates[$dateType] ?? NULL;
+          if (empty($memParams[$dateType])) {
+            $memParams[$dateType] = $dates[$dateType] ?? NULL;
+          }
+        }
+
+        $status = CRM_Member_BAO_MembershipStatus::getMembershipStatusByDate(CRM_Utils_Date::customFormat($dates['start_date'],
+          $statusFormat
+        ),
+          CRM_Utils_Date::customFormat($dates['end_date'],
+            $statusFormat
+          ),
+          CRM_Utils_Date::customFormat($dates['join_date'],
+            $statusFormat
+          ),
+          'today',
+          TRUE,
+          $membershipTypeID,
+          $memParams
+        );
+        $updateStatusId = $status['id'] ?? NULL;
+      }
+      else {
+        // if IPN/Pay-Later set status to: PENDING
+        $updateStatusId = array_search('Pending', $allStatus);
+      }
+
+      if (!empty($membershipSource)) {
+        $memParams['source'] = $membershipSource;
+      }
+      $memParams['is_test'] = $is_test;
+      $memParams['is_pay_later'] = $isPayLater;
+    }
+    // Putting this in an IF is precautionary as it seems likely that it would be ignored if empty, but
+    // perhaps shouldn't be?
+    if ($contributionRecurID) {
+      $memParams['contribution_recur_id'] = $contributionRecurID;
+    }
+    //CRM-4555
+    //if we decided status here and want to skip status
+    //calculation in create( ); then need to pass 'skipStatusCal'.
+    if ($updateStatusId) {
+      $memParams['status_id'] = $updateStatusId;
+      $memParams['skipStatusCal'] = TRUE;
+    }
+
+    //since we are renewing,
+    //make status override false.
+    $memParams['is_override'] = FALSE;
+
+    //CRM-4027, create log w/ individual contact.
+    if ($modifiedID) {
+      // @todo this param is likely unused now.
+      $memParams['is_for_organization'] = TRUE;
+    }
+    $params['modified_id'] = $modifiedID ?? $contactID;
+
+    //inherit campaign from contrib page.
+    if (isset($campaignId)) {
+      $memParams['campaign_id'] = $campaignId;
+    }
+
+    $memParams['contribution'] = $contribution;
+    $memParams['custom'] = $customFieldsFormatted;
+    // Load all line items & process all in membership. Don't do in contribution.
+    // Relevant tests in api_v3_ContributionPageTest.
+    $memParams['line_item'] = $lineItems;
+    // @todo stop passing $ids (membership and userId may be set by this point)
+    $membership = CRM_Member_BAO_Membership::create($memParams, $ids);
+
+    // not sure why this statement is here, seems quite odd :( - Lobo: 12/26/2010
+    // related to: http://forum.civicrm.org/index.php/topic,11416.msg49072.html#msg49072
+    $membership->find(TRUE);
+
+    return [$membership, $renewalMode, $dates];
+  }
+
 }