diff --git a/src/Entity/Service.php b/src/Entity/Service.php
index 137753d..0f8c190 100644
--- a/src/Entity/Service.php
+++ b/src/Entity/Service.php
@@ -17,6 +17,7 @@ class Service implements NodeInterface
     const S_3DAYSELECT = '12';
     const S_GROUND = '03';
     const S_SURE_POST = '93';
+    const S_MAIL_INNOVATIONS = 'M4';
 
     // Valid international values
     const S_STANDARD = '11';
@@ -106,6 +107,7 @@ class Service implements NodeInterface
         '74' => 'UPS Express 12:00',
         '93' => 'UPS Sure Post',
         '96' => 'UPS Worldwide Express Freight',
+        'M4' => 'UPS Mail Innovations',
     ];
 
     /** @deprecated */
diff --git a/src/Entity/Shipment.php b/src/Entity/Shipment.php
index 8985482..670f692 100644
--- a/src/Entity/Shipment.php
+++ b/src/Entity/Shipment.php
@@ -4,6 +4,11 @@
 
 class Shipment
 {
+    const USPS_ENDORSEMENT_RETURN_SERVICE = 1;
+    const USPS_ENDORSEMENT_FORWARDING_SERVICE = 2;
+    const USPS_ENDORSEMENT_ADDRESS_SERVICE = 3;
+    const USPS_ENDORSEMENT_CHANGE_SERVICE = 4;
+    const USPS_ENDORSEMENT_NO_SERVICE = 5;
     /**
      * @var PaymentInformation
      */
@@ -122,6 +127,18 @@ class Shipment
      * @var bool
      */
     private $taxInformationIndicator;
+    
+    /**
+     * Required for Mail Innovations.
+     * @var integer 
+     */
+    private $uspsEndorsement;
+
+    /**
+     * Required for Mail Innovations.
+     * @var string 
+     */
+    private $packageId;
 
     public function __construct()
     {
@@ -610,4 +627,44 @@ public function setTaxInformationIndicator(bool $taxInformationIndicator): self
         
         return $this;
     }
+    
+    /**
+     * @return int $uspsEndorsement
+     */
+    public function getUSPSEndorsement()
+    {
+        return $this->uspsEndorsement;
+    }
+
+    /**
+     * @param integer $uspsEndorsement
+     *
+     * @return Shipment
+     */
+    public function setUSPSEndorsement($uspsEndorsement)
+    {
+        $this->uspsEndorsement = $uspsEndorsement;
+
+        return $this;
+    }
+
+    /**
+     * @return int $packageId
+     */
+    public function getPackageId()
+    {
+        return $this->packageId;
+    }
+
+    /**
+     * @param integer $packageId
+     *
+     * @return Shipment
+     */
+    public function setPackageId($packageId)
+    {
+        $this->packageId = $packageId;
+        
+        return $this;
+    }
 }
diff --git a/src/Shipping.php b/src/Shipping.php
index 04ee831..3fcc6ce 100644
--- a/src/Shipping.php
+++ b/src/Shipping.php
@@ -132,6 +132,14 @@ private function createConfirmRequest(
         if ($shipment->getDescription()) {
             $shipmentNode->appendChild($xml->createElement('Description', $shipment->getDescription()));
         }
+        
+        if ($shipment->getUspsEndorsement()) {
+            $shipmentNode->appendChild($xml->createElement('USPSEndorsement', $shipment->getUSPSEndorsement()));
+        }
+
+        if ($shipment->getPackageId()) {
+            $shipmentNode->appendChild($xml->createElement('PackageID', $shipment->getPackageId()));
+        }
 
         $returnService = $shipment->getReturnService();
         if (isset($returnService)) {