diff --git a/vendor/magento/module-inventory-sales/Model/GetBackorder.php b/vendor/magento/module-inventory-sales/Model/GetBackorder.php
new file mode 100644
index 000000000000..06d0ca64a3fb
--- /dev/null
+++ b/vendor/magento/module-inventory-sales/Model/GetBackorder.php
@@ -0,0 +1,187 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\InventorySales\Model;
+
+use Magento\Framework\App\ObjectManager;
+use Magento\Framework\DataObject;
+use Magento\Framework\DataObject\Factory as ObjectFactory;
+use Magento\Framework\Exception\LocalizedException;
+use Magento\Framework\Exception\NoSuchEntityException;
+use Magento\Framework\Locale\FormatInterface;
+use Magento\InventoryCatalogApi\Model\GetSkusByProductIdsInterface;
+use Magento\InventorySales\Model\IsProductSalableCondition\BackOrderNotifyCustomerCondition;
+use Magento\InventorySales\Model\IsProductSalableForRequestedQtyCondition\ProductSalabilityError;
+use Magento\InventorySalesApi\Api\AreProductsSalableForRequestedQtyInterface;
+use Magento\InventorySalesApi\Api\Data\IsProductSalableForRequestedQtyRequestInterfaceFactory;
+use Magento\InventorySalesApi\Api\Data\SalesChannelInterface;
+use Magento\InventorySalesApi\Api\StockResolverInterface;
+use Magento\Store\Model\StoreManagerInterface;
+
+/**
+ * Backorder class
+ *
+ * Returns the backorder qty based on product id and stock id
+ * @SuppressWarnings(PHPMD.CouplingBetweenObjects)
+ */
+class GetBackorder
+{
+    /**
+     * @var ObjectFactory
+     */
+    private $objectFactory;
+
+    /**
+     * @var FormatInterface
+     */
+    private $format;
+
+    /**
+     * @var AreProductsSalableForRequestedQtyInterface
+     */
+    private $areProductsSalableForRequestedQty;
+
+    /**
+     * @var IsProductSalableForRequestedQtyRequestInterfaceFactory
+     */
+    private $isProductSalableForRequestedQtyRequestInterfaceFactory;
+
+    /**
+     * @var GetSkusByProductIdsInterface
+     */
+    private $getSkusByProductIds;
+
+    /**
+     * @var StockResolverInterface
+     */
+    private $stockResolver;
+
+    /**
+     * @var StoreManagerInterface
+     */
+    private $storeManager;
+
+    /**
+     * @var BackOrderNotifyCustomerCondition
+     */
+    private $backOrderNotifyCustomerCondition;
+
+    /**
+     * @var GetBackorderQty
+     */
+    private $getBackorderQty;
+
+    /**
+     * @param ObjectFactory $objectFactory
+     * @param FormatInterface $format
+     * @param AreProductsSalableForRequestedQtyInterface $areProductsSalableForRequestedQty
+     * @param IsProductSalableForRequestedQtyRequestInterfaceFactory $isProductSalableForRequestedQtyRequestFactory
+     * @param GetSkusByProductIdsInterface $getSkusByProductIds
+     * @param StockResolverInterface $stockResolver
+     * @param StoreManagerInterface $storeManager
+     * @param BackOrderNotifyCustomerCondition $backOrderNotifyCustomerCondition
+     * @param GetBackorderQty|null $getBackorderQty
+     * @SuppressWarnings(PHPMD.LongVariable)
+     */
+    public function __construct(
+        ObjectFactory $objectFactory,
+        FormatInterface $format,
+        AreProductsSalableForRequestedQtyInterface $areProductsSalableForRequestedQty,
+        IsProductSalableForRequestedQtyRequestInterfaceFactory $isProductSalableForRequestedQtyRequestFactory,
+        GetSkusByProductIdsInterface $getSkusByProductIds,
+        StockResolverInterface $stockResolver,
+        StoreManagerInterface $storeManager,
+        BackOrderNotifyCustomerCondition $backOrderNotifyCustomerCondition,
+        GetBackorderQty $getBackorderQty = null
+    ) {
+        $this->objectFactory = $objectFactory;
+        $this->format = $format;
+        $this->getSkusByProductIds = $getSkusByProductIds;
+        $this->storeManager = $storeManager;
+        $this->stockResolver = $stockResolver;
+        $this->isProductSalableForRequestedQtyRequestInterfaceFactory = $isProductSalableForRequestedQtyRequestFactory;
+        $this->areProductsSalableForRequestedQty = $areProductsSalableForRequestedQty;
+        $this->backOrderNotifyCustomerCondition = $backOrderNotifyCustomerCondition;
+        $this->getBackorderQty = $getBackorderQty
+            ?? ObjectManager::getInstance()->get(GetBackorderQty::class);
+    }
+
+    /**
+     * Main execute function
+     *
+     * @param int $productId
+     * @param int|float $itemQty
+     * @param int|float $qtyToCheck
+     * @param int|null $scopeId
+     *
+     * @return DataObject
+     * @throws LocalizedException
+     * @throws NoSuchEntityException
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function execute(int $productId, $itemQty, $qtyToCheck, $scopeId): object
+    {
+        $result = $this->objectFactory->create();
+        $result->setHasError(false);
+
+        $qty = max($this->getNumber($itemQty), $this->getNumber($qtyToCheck));
+
+        $skus = $this->getSkusByProductIds->execute([$productId]);
+        $productSku = $skus[$productId];
+
+        $websiteCode = $this->storeManager->getWebsite($scopeId)->getCode();
+        $stock = $this->stockResolver->execute(SalesChannelInterface::TYPE_WEBSITE, $websiteCode);
+        $stockId = $stock->getStockId();
+
+        $request = $this->isProductSalableForRequestedQtyRequestInterfaceFactory->create(
+            [
+                'sku' => $productSku,
+                'qty' => $qty,
+            ]
+        );
+        $productsSalableResult = $this->areProductsSalableForRequestedQty->execute([$request], (int)$stockId);
+        $productsSalableResult = current($productsSalableResult);
+
+        if ($productsSalableResult->isSalable() === false) {
+            /** @var ProductSalabilityError $error */
+            foreach ($productsSalableResult->getErrors() as $error) {
+                $result->setHasError(true)->setMessage($error->getMessage())->setQuoteMessage($error->getMessage())
+                    ->setQuoteMessageIndex('qty')->setErrorCode($error->getCode());
+            }
+        } else {
+            $productSalableResult = $this->backOrderNotifyCustomerCondition->execute($productSku, (int)$stockId, $qty);
+            if ($productSalableResult->getErrors()) {
+                /** @var ProductSalabilityError $error */
+                foreach ($productSalableResult->getErrors() as $error) {
+                    $result->setMessage($error->getMessage());
+                }
+            }
+            $backorderQty = $this->getBackorderQty->execute($productSku, (int)$stockId, $qty);
+            if ($backorderQty > 0) {
+                $result->setItemBackorders($backorderQty);
+            }
+        }
+
+        return $result;
+    }
+
+    /**
+     * Convert quantity to a valid float
+     *
+     * @param int|float $qty
+     *
+     * @return float
+     */
+    private function getNumber($qty): float
+    {
+        if (!is_numeric($qty)) {
+            return $this->format->getNumber($qty);
+        }
+
+        return $qty;
+    }
+}
\ No newline at end of file
diff --git a/vendor/magento/module-inventory-sales/Model/GetBackorderQty.php b/vendor/magento/module-inventory-sales/Model/GetBackorderQty.php
new file mode 100644
index 000000000000..f821288389a7
--- /dev/null
+++ b/vendor/magento/module-inventory-sales/Model/GetBackorderQty.php
@@ -0,0 +1,120 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\InventorySales\Model;
+
+use Magento\InventorySalesApi\Model\GetStockItemDataInterface;
+use Magento\InventoryConfigurationApi\Api\GetStockItemConfigurationInterface;
+use Magento\InventoryConfigurationApi\Api\Data\StockItemConfigurationInterface;
+use Magento\InventorySalesApi\Api\GetProductSalableQtyInterface;
+
+/**
+ * GetBackorderQty class
+ *
+ * Returns the amount of items to be backordered, based on the product sku, stockId
+ * and requested quantity
+ */
+class GetBackorderQty
+{
+    /**
+     * @var GetStockItemConfigurationInterface
+     */
+    private $getStockItemConfiguration;
+
+    /**
+     * @var GetStockItemDataInterface
+     */
+    private $getStockItemData;
+
+    /**
+     * @var GetProductSalableQtyInterface
+     */
+    private $getProductSalableQty;
+
+    /**
+     * @param GetStockItemConfigurationInterface $getStockItemConfig
+     * @param GetStockItemDataInterface $getStockItemData
+     * @param GetProductSalableQtyInterface $getProductSalableQty
+     */
+    public function __construct(
+        GetStockItemConfigurationInterface $getStockItemConfig,
+        GetStockItemDataInterface $getStockItemData,
+        GetProductSalableQtyInterface $getProductSalableQty
+    ) {
+        $this->getStockItemConfiguration = $getStockItemConfig;
+        $this->getStockItemData = $getStockItemData;
+        $this->getProductSalableQty = $getProductSalableQty;
+    }
+
+    /**
+     * Main execute function
+     *
+     * Calculate the amount of a particular product that is to be backordered based on the
+     * salable quantity available, given its sku, stockId and the amount requested.
+     *
+     * @param string $sku
+     * @param integer $stockId
+     * @param float $requestedQty
+     * @return float
+     */
+    public function execute(string $sku, int $stockId, float $requestedQty): float
+    {
+        $stockItemConfiguration = $this->getStockItemConfiguration->execute($sku, $stockId);
+        $backOrderQty = 0;
+
+        if ($stockItemConfiguration->isManageStock()
+            && ($stockItemConfiguration->getBackorders() === StockItemConfigurationInterface::BACKORDERS_YES_NOTIFY ||
+                $stockItemConfiguration->getBackorders() === StockItemConfigurationInterface::BACKORDERS_YES_NONOTIFY)
+        ) {
+            $stockItemData = $this->getStockItemData->execute($sku, $stockId);
+            if (null === $stockItemData) {
+                return $backOrderQty;
+            }
+
+            $salableQty = $this->getProductSalableQty->execute($sku, $stockId);
+            /**
+             * Salable Quantity has had minQty subtracted from it. This means that when minqty is a negative value
+             * it is increasing the value of salable quantity to incorporate the fact that we are allowed to sell
+             * more items than in stock. When calculating backorder quantity to be displayed to customer and to be
+             * logged in sales_order_item, we don't want salable qty to include this, we want the backorder qty to
+             * indicate how many more items than we have in stock are being ordered including any existing
+             * reservations.
+             *
+             * Example calculation
+             *
+             * instock = 10
+             * minqty = -10
+             *
+             * Therefore $salableQty = 20
+             *
+             * $requestedQty = 15
+             *
+             * Therefore the amount to be backordered would be 15 - 20 - (-10) = 5
+             */
+            $minqty = $stockItemConfiguration->getMinQty();
+            $backOrderQty = $requestedQty - $salableQty - $minqty;
+            /**
+             * In cases of more stock available than being ordered, the above calculation returns a
+             * negative result indicating more stock available than requested. Set to zero in this case
+             */
+            if ($backOrderQty < 0) {
+                $backOrderQty = 0;
+            }
+            /**
+             * Catch the situation where we are already in backorders. e.g 0 in stock, reservations already
+             * in for 5 items on other orders, and we get a request for 5 more. Without this check, we would
+             * end up notifying the customer that 10 needed to be backorderd (10 backorderd items are required
+             * to satisfy this order plus all reservations), but only 5 of them are relevant to this
+             * request/customer/order so always cap the backOrderQty to the amount requested.
+             */
+            if (bccomp((string)$requestedQty, (string)$backOrderQty, 4) < 0) {
+                $backOrderQty = $requestedQty;
+            }
+        }
+        return $backOrderQty;
+    }
+}
diff --git a/vendor/magento/module-inventory-sales/Model/IsProductSalableCondition/BackOrderNotifyCustomerCondition.php b/vendor/magento/module-inventory-sales/Model/IsProductSalableCondition/BackOrderNotifyCustomerCondition.php
index ea24fb973ca4..45cb6dcddaf5 100644
--- a/vendor/magento/module-inventory-sales/Model/IsProductSalableCondition/BackOrderNotifyCustomerCondition.php
+++ b/vendor/magento/module-inventory-sales/Model/IsProductSalableCondition/BackOrderNotifyCustomerCondition.php
@@ -16,6 +16,7 @@
 use Magento\InventorySalesApi\Api\IsProductSalableForRequestedQtyInterface;
 use Magento\InventorySalesApi\Model\GetStockItemDataInterface;
 use Magento\InventorySalesApi\Api\GetProductSalableQtyInterface;
+use Magento\InventorySales\Model\GetBackorderQty;
 
 /**
  * Get back order notify for customer condition
@@ -29,46 +30,43 @@ class BackOrderNotifyCustomerCondition implements IsProductSalableForRequestedQt
      */
     private $getStockItemConfiguration;
 
-    /**
-     * @var GetStockItemDataInterface
-     */
-    private $getStockItemData;
-
     /**
      * @var ProductSalableResultInterfaceFactory
      */
     private $productSalableResultFactory;
 
     /**
-     * @var GetProductSalableQtyInterface
+     * @var ProductSalabilityErrorInterfaceFactory
      */
-    private $getProductSalableQty;
+    private $productSalabilityErrorFactory;
 
     /**
-     * @var ProductSalabilityErrorInterfaceFactory
+     * @var GetBackorderQty
      */
-    private $productSalabilityErrorFactory;
+    private $getBackorderQty;
 
     /**
      * @param GetStockItemConfigurationInterface $getStockItemConfiguration
-     * @param GetStockItemDataInterface $getStockItemData
+     * @param GetStockItemDataInterface $getStockItemData @deprecated
      * @param ProductSalableResultInterfaceFactory $productSalableResultFactory
      * @param ProductSalabilityErrorInterfaceFactory $productSalabilityErrorFactory
-     * @param GetProductSalableQtyInterface|null $getProductSalableQty
+     * @param GetProductSalableQtyInterface|null $getProductSalableQty @deprecated
+     * @param GetBackorderQty|null $getBackorderQty
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
      */
     public function __construct(
         GetStockItemConfigurationInterface $getStockItemConfiguration,
         GetStockItemDataInterface $getStockItemData,
         ProductSalableResultInterfaceFactory $productSalableResultFactory,
         ProductSalabilityErrorInterfaceFactory $productSalabilityErrorFactory,
-        ?GetProductSalableQtyInterface $getProductSalableQty = null
+        ?GetProductSalableQtyInterface $getProductSalableQty = null,
+        ?GetBackorderQty $getBackorderQty = null
     ) {
         $this->getStockItemConfiguration = $getStockItemConfiguration;
-        $this->getStockItemData = $getStockItemData;
         $this->productSalableResultFactory = $productSalableResultFactory;
         $this->productSalabilityErrorFactory = $productSalabilityErrorFactory;
-        $this->getProductSalableQty = $getProductSalableQty
-            ?? ObjectManager::getInstance()->get(GetProductSalableQtyInterface::class);
+        $this->getBackorderQty = $getBackorderQty
+            ?? ObjectManager::getInstance()->get(GetBackorderQty::class);
     }
 
     /**
@@ -81,23 +79,17 @@ public function execute(string $sku, int $stockId, float $requestedQty): Product
         if ($stockItemConfiguration->isManageStock()
             && $stockItemConfiguration->getBackorders() === StockItemConfigurationInterface::BACKORDERS_YES_NOTIFY
         ) {
-            $stockItemData = $this->getStockItemData->execute($sku, $stockId);
-            if (null === $stockItemData) {
-                return $this->productSalableResultFactory->create(['errors' => []]);
-            }
-            $salableQty = $this->getProductSalableQty->execute($sku, $stockId);
-            $remainingQty = ($salableQty > $requestedQty) ? $salableQty - $requestedQty : $requestedQty - $salableQty;
-            $displayQty = $this->getDisplayQty($remainingQty, $salableQty, $requestedQty);
+            $backorderQty = $this->getBackorderQty->execute($sku, $stockId, $requestedQty);
 
-            if ($requestedQty > $stockItemData[GetStockItemDataInterface::QUANTITY] && $displayQty >= 0) {
+            if ($backorderQty > 0) {
                 $errors = [
                     $this->productSalabilityErrorFactory->create([
-                            'code' => 'back_order-not-enough',
-                            'message' => __(
-                                'We don\'t have as many quantity as you requested, '
-                                . 'but we\'ll back order the remaining %1.',
-                                $displayQty * 1
-                            )])
+                        'code' => 'back_order-not-enough',
+                        'message' => __(
+                            'We don\'t have as many quantity as you requested, '
+                            . 'but we\'ll back order the remaining %1.',
+                            $backorderQty * 1
+                        )])
                 ];
                 return $this->productSalableResultFactory->create(['errors' => $errors]);
             }
@@ -105,23 +97,4 @@ public function execute(string $sku, int $stockId, float $requestedQty): Product
 
         return $this->productSalableResultFactory->create(['errors' => []]);
     }
-
-    /**
-     * Get display quantity to show the number of quantity customer can backorder
-     *
-     * @param float $remainingQty
-     * @param float $salableQty
-     * @param float $requestedQty
-     * @return float
-     */
-    private function getDisplayQty(float $remainingQty, float $salableQty, float $requestedQty): float
-    {
-        $displayQty = 0;
-        if ($remainingQty > 0 && $salableQty > 0) {
-            $displayQty = $remainingQty;
-        } elseif ($requestedQty > $salableQty) {
-            $displayQty = $requestedQty;
-        }
-        return $displayQty;
-    }
-}
+}
\ No newline at end of file
diff --git a/vendor/magento/module-inventory-sales/Plugin/StockState/CheckQuoteItemQtyPlugin.php b/vendor/magento/module-inventory-sales/Plugin/StockState/CheckQuoteItemQtyPlugin.php
index c4210e65b1db..7b105ca459af 100644
--- a/vendor/magento/module-inventory-sales/Plugin/StockState/CheckQuoteItemQtyPlugin.php
+++ b/vendor/magento/module-inventory-sales/Plugin/StockState/CheckQuoteItemQtyPlugin.php
@@ -7,20 +7,12 @@
 
 namespace Magento\InventorySales\Plugin\StockState;
 
+use Magento\Framework\App\ObjectManager;
 use Magento\CatalogInventory\Api\StockStateInterface;
 use Magento\Framework\DataObject;
-use Magento\Framework\DataObject\Factory as ObjectFactory;
 use Magento\Framework\Exception\LocalizedException;
 use Magento\Framework\Exception\NoSuchEntityException;
-use Magento\Framework\Locale\FormatInterface;
-use Magento\InventoryCatalogApi\Model\GetSkusByProductIdsInterface;
-use Magento\InventorySales\Model\IsProductSalableCondition\BackOrderNotifyCustomerCondition;
-use Magento\InventorySales\Model\IsProductSalableForRequestedQtyCondition\ProductSalabilityError;
-use Magento\InventorySalesApi\Api\AreProductsSalableForRequestedQtyInterface;
-use Magento\InventorySalesApi\Api\Data\IsProductSalableForRequestedQtyRequestInterfaceFactory;
-use Magento\InventorySalesApi\Api\Data\SalesChannelInterface;
-use Magento\InventorySalesApi\Api\StockResolverInterface;
-use Magento\Store\Model\StoreManagerInterface;
+use Magento\InventorySales\Model\GetBackorder;
 
 /**
  * Replace legacy quote item check
@@ -29,74 +21,18 @@
 class CheckQuoteItemQtyPlugin
 {
     /**
-     * @var ObjectFactory
+     * @var GetBackorder
      */
-    private $objectFactory;
+    private $getBackorder;
 
     /**
-     * @var FormatInterface
-     */
-    private $format;
-
-    /**
-     * @var AreProductsSalableForRequestedQtyInterface
-     */
-    private $areProductsSalableForRequestedQty;
-
-    /**
-     * @var IsProductSalableForRequestedQtyRequestInterfaceFactory
-     */
-    private $isProductSalableForRequestedQtyRequestInterfaceFactory;
-
-    /**
-     * @var GetSkusByProductIdsInterface
-     */
-    private $getSkusByProductIds;
-
-    /**
-     * @var StockResolverInterface
-     */
-    private $stockResolver;
-
-    /**
-     * @var StoreManagerInterface
-     */
-    private $storeManager;
-
-    /**
-     * @var BackOrderNotifyCustomerCondition
-     */
-    private $backOrderNotifyCustomerCondition;
-
-    /**
-     * @param ObjectFactory $objectFactory
-     * @param FormatInterface $format
-     * @param AreProductsSalableForRequestedQtyInterface $areProductsSalableForRequestedQty
-     * @param IsProductSalableForRequestedQtyRequestInterfaceFactory $isProductSalableForRequestedQtyRequestFactory
-     * @param GetSkusByProductIdsInterface $getSkusByProductIds
-     * @param StockResolverInterface $stockResolver
-     * @param StoreManagerInterface $storeManager
-     * @param BackOrderNotifyCustomerCondition $backOrderNotifyCustomerCondition
-     * @SuppressWarnings(PHPMD.LongVariable)
+     * @param GetBackorder|null $getBackorder
      */
     public function __construct(
-        ObjectFactory $objectFactory,
-        FormatInterface $format,
-        AreProductsSalableForRequestedQtyInterface $areProductsSalableForRequestedQty,
-        IsProductSalableForRequestedQtyRequestInterfaceFactory $isProductSalableForRequestedQtyRequestFactory,
-        GetSkusByProductIdsInterface $getSkusByProductIds,
-        StockResolverInterface $stockResolver,
-        StoreManagerInterface $storeManager,
-        BackOrderNotifyCustomerCondition $backOrderNotifyCustomerCondition
+        GetBackorder $getBackorder = null
     ) {
-        $this->objectFactory = $objectFactory;
-        $this->format = $format;
-        $this->areProductsSalableForRequestedQty = $areProductsSalableForRequestedQty;
-        $this->isProductSalableForRequestedQtyRequestInterfaceFactory = $isProductSalableForRequestedQtyRequestFactory;
-        $this->getSkusByProductIds = $getSkusByProductIds;
-        $this->stockResolver = $stockResolver;
-        $this->storeManager = $storeManager;
-        $this->backOrderNotifyCustomerCondition = $backOrderNotifyCustomerCondition;
+        $this->getBackorder = $getBackorder
+            ?? ObjectManager::getInstance()->get(GetBackorder::class);
     }
 
     /**
@@ -124,62 +60,6 @@ public function aroundCheckQuoteItemQty(
         $origQty,
         $scopeId = null
     ) {
-        $result = $this->objectFactory->create();
-        $result->setHasError(false);
-
-        $qty = max($this->getNumber($itemQty), $this->getNumber($qtyToCheck));
-
-        $skus = $this->getSkusByProductIds->execute([$productId]);
-        $productSku = $skus[$productId];
-
-        $websiteCode = $this->storeManager->getWebsite($scopeId)->getCode();
-        $stock = $this->stockResolver->execute(SalesChannelInterface::TYPE_WEBSITE, $websiteCode);
-        $stockId = $stock->getStockId();
-
-        $request = $this->isProductSalableForRequestedQtyRequestInterfaceFactory->create(
-            [
-                'sku' => $productSku,
-                'qty' => $qty,
-            ]
-        );
-        $productsSalableResult = $this->areProductsSalableForRequestedQty->execute([$request], (int)$stockId);
-        $productsSalableResult = current($productsSalableResult);
-
-        if ($productsSalableResult->isSalable() === false) {
-            /** @var ProductSalabilityError $error */
-            foreach ($productsSalableResult->getErrors() as $error) {
-                $result->setHasError(true)
-                    ->setMessage($error->getMessage())
-                    ->setQuoteMessage($error->getMessage())
-                    ->setQuoteMessageIndex('qty')
-                    ->setErrorCode($error->getCode());
-            }
-        } else {
-            $productSalableResult = $this->backOrderNotifyCustomerCondition->execute($productSku, (int)$stockId, $qty);
-            if ($productSalableResult->getErrors()) {
-                /** @var ProductSalabilityError $error */
-                foreach ($productSalableResult->getErrors() as $error) {
-                    $result->setMessage($error->getMessage());
-                }
-            }
-        }
-
-        return $result;
-    }
-
-    /**
-     * Convert quantity to a valid float
-     *
-     * @param string|float|int|null $qty
-     *
-     * @return float|null
-     */
-    private function getNumber($qty)
-    {
-        if (!is_numeric($qty)) {
-            return $this->format->getNumber($qty);
-        }
-
-        return $qty;
+        return $this->getBackorder->execute((int) $productId, $itemQty, $qtyToCheck, $scopeId);
     }
-}
+}
\ No newline at end of file
diff --git a/vendor/magento/module-inventory-sales/Plugin/StockStateProvider/CheckQuoteItemQtyPlugin.php b/vendor/magento/module-inventory-sales/Plugin/StockStateProvider/CheckQuoteItemQtyPlugin.php
new file mode 100644
index 000000000000..aee35b748005
--- /dev/null
+++ b/vendor/magento/module-inventory-sales/Plugin/StockStateProvider/CheckQuoteItemQtyPlugin.php
@@ -0,0 +1,104 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\InventorySales\Plugin\StockStateProvider;
+
+use Magento\Catalog\Model\Product\Type;
+use Magento\CatalogInventory\Api\Data\StockItemInterface;
+use Magento\CatalogInventory\Model\Spi\StockStateProviderInterface;
+use Magento\Framework\App\ObjectManager;
+use Magento\Framework\DataObject;
+use Magento\Framework\DataObject\Factory as ObjectFactory;
+use Magento\Framework\Exception\LocalizedException;
+use Magento\Framework\Exception\NoSuchEntityException;
+use Magento\InventoryCatalogApi\Model\GetProductTypesBySkusInterface;
+use Magento\InventoryCatalogApi\Model\GetSkusByProductIdsInterface;
+use Magento\InventorySales\Model\GetBackorder;
+
+/**
+ * Replace legacy quote item check
+ * @SuppressWarnings(PHPMD.CouplingBetweenObjects)
+ */
+class CheckQuoteItemQtyPlugin
+{
+    /**
+     * @var ObjectFactory
+     */
+    private $objectFactory;
+
+    /**
+     * @var GetProductTypesBySkusInterface
+     */
+    private $getProductTypesBySkus;
+
+    /**
+     * @var GetSkusByProductIdsInterface
+     */
+    private $getSkusByProductIds;
+
+    /**
+     * @var GetBackorder
+     */
+    private $getBackorder;
+
+    /**
+     * @param ObjectFactory|null $objectFactory
+     * @param GetProductTypesBySkusInterface|null $getProductTypesBySkus
+     * @param GetSkusByProductIdsInterface|null $getSkusByProductIds
+     * @param GetBackorder|null $getBackorder
+     */
+    public function __construct(
+        ObjectFactory $objectFactory = null,
+        GetProductTypesBySkusInterface $getProductTypesBySkus = null,
+        GetSkusByProductIdsInterface $getSkusByProductIds = null,
+        GetBackorder $getBackorder = null
+    ) {
+        $this->objectFactory = $objectFactory
+            ?? ObjectManager::getInstance()->get(ObjectFactory::class);
+        $this->getProductTypesBySkus = $getProductTypesBySkus
+            ?? ObjectManager::getInstance()->get(GetProductTypesBySkusInterface::class);
+        $this->getSkusByProductIds = $getSkusByProductIds
+            ?? ObjectManager::getInstance()->get(GetSkusByProductIdsInterface::class);
+        $this->getBackorder = $getBackorder
+            ?? ObjectManager::getInstance()->get(GetBackorder::class);
+    }
+
+    /**
+     * Replace legacy quote item check
+     *
+     * @param StockStateProviderInterface $subject
+     * @param \Closure $proceed
+     * @param StockItemInterface $stockItem
+     * @param int|float $itemQty
+     * @param int|float $qtyToCheck
+     * @param int|float $origQty
+     *
+     * @return DataObject
+     * @throws LocalizedException
+     * @throws NoSuchEntityException
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function aroundCheckQuoteItemQty(
+        StockStateProviderInterface $subject,
+        \Closure $proceed,
+        StockItemInterface $stockItem,
+        $itemQty,
+        $qtyToCheck,
+        $origQty = 0
+    ) {
+        $productId = $stockItem->getProductId();
+        $skus = $this->getSkusByProductIds->execute([$productId]);
+        $productSku = $skus[$productId];
+        $productType = $this->getProductTypesBySkus->execute([$productSku])[$productSku];
+        if ($productType !== Type::TYPE_SIMPLE) {
+            $result = $this->objectFactory->create();
+            $result->setHasError(false);
+            return $result;
+        }
+        return $this->getBackorder->execute((int) $productId, $itemQty, $qtyToCheck, null);
+    }
+}
diff --git a/vendor/magento/module-inventory-sales/etc/di.xml b/vendor/magento/module-inventory-sales/etc/di.xml
index 12b95a877435..7921fb927a2f 100644
--- a/vendor/magento/module-inventory-sales/etc/di.xml
+++ b/vendor/magento/module-inventory-sales/etc/di.xml
@@ -25,6 +25,9 @@
         <plugin name="check_quote_item_qty" type="Magento\InventorySales\Plugin\StockState\CheckQuoteItemQtyPlugin"/>
         <plugin name="suggest_qty" type="Magento\InventorySales\Plugin\StockState\SuggestQtyPlugin"/>
     </type>
+    <type name="Magento\CatalogInventory\Model\Spi\StockStateProviderInterface">
+        <plugin name="check_quote_item_qty" type="Magento\InventorySales\Plugin\StockStateProvider\CheckQuoteItemQtyPlugin" sortOrder="20"/>
+    </type>
     <type name="Magento\InventoryReservationsApi\Model\AppendReservationsInterface">
         <plugin name="prevent_append_reservation_on_not_manage_items_in_stock" type="Magento\InventorySales\Plugin\InventoryReservationsApi\PreventAppendReservationOnNotManageItemsInStockPlugin"/>
     </type>
@@ -200,4 +203,4 @@
     <preference for="Magento\InventorySalesApi\Api\Data\IsProductSalableForRequestedQtyRequestInterface" type="Magento\InventorySales\Model\IsProductSalableForRequestedQtyRequest"/>
     <preference for="Magento\InventorySalesApi\Api\Data\IsProductSalableForRequestedQtyResultInterface" type="Magento\InventorySales\Model\IsProductSalableForRequestedQtyResult"/>
     <preference for="Magento\InventorySalesApi\Api\Data\IsProductSalableResultInterface" type="Magento\InventorySales\Model\IsProductSalableResult"/>
-</config>
+</config>
\ No newline at end of file