diff --git a/src/Controller/JobOrderController.php b/src/Controller/JobOrderController.php
index 2ed5ea96..7c37fc7e 100644
--- a/src/Controller/JobOrderController.php
+++ b/src/Controller/JobOrderController.php
@@ -656,31 +656,33 @@ class JobOrderController extends BaseController
     protected function invoiceBatteries($em, InvoiceCriteria $criteria, $items)
     {
         // return error if there's a problem, false otherwise
-
-        foreach ($items as $item)
+        if (!empty($items)) 
         {
-            // check if this is a valid battery
-            $battery = $em->getRepository(Battery::class)->find($item['battery']);
-
-            if (empty($battery))
+            foreach ($items as $item)
             {
-                $error = 'Invalid battery specified.';
-                return $error;
+                // check if this is a valid battery
+                $battery = $em->getRepository(Battery::class)->find($item['battery']);
+
+                if (empty($battery))
+                {
+                    $error = 'Invalid battery specified.';
+                    return $error;
+                }
+
+                // quantity
+                $qty = $item['quantity'];
+                if ($qty < 1)
+                    continue;
+
+                // add to criteria
+                $criteria->addBattery($battery, $qty);
+
+                // if this is a trade in, add trade in
+                if (!empty($item['trade_in']) && TradeInType::validate($item['trade_in']))
+                    $criteria->addTradeIn($item['trade_in'] == 'motolite', $qty);
             }
-
-            // quantity
-            $qty = $item['quantity'];
-            if ($qty < 1)
-                continue;
-
-            // add to criteria
-            $criteria->addBattery($battery, $qty);
-
-            // if this is a trade in, add trade in
-            if (!empty($item['trade_in']) && TradeInType::validate($item['trade_in']))
-                $criteria->addTradeIn($item['trade_in'] == 'motolite', $qty);
         }
-
+            
         return null;
     }
 
@@ -700,7 +702,6 @@ class JobOrderController extends BaseController
 
         if (!$error)
             $error = $this->invoiceBatteries($em, $criteria, $items);
-            
 
         if ($error)
         {
diff --git a/templates/job-order/form.html.twig b/templates/job-order/form.html.twig
index 5d6950c1..9d3987ec 100644
--- a/templates/job-order/form.html.twig
+++ b/templates/job-order/form.html.twig
@@ -921,6 +921,11 @@ $(function() {
 		generateInvoice();
 	});
 
+	// update invoice when promo is changed
+	$("#invoice-promo").change(function() {
+		generateInvoice();
+	});
+
 	function generateInvoice() {
 		var promo = $("#invoice-promo").val();
 		var table = $("#invoice-table tbody");