diff --git a/src/Config/ConfigInterface.php b/src/Config/ConfigInterface.php
index 821589e..1b3d6f1 100644
--- a/src/Config/ConfigInterface.php
+++ b/src/Config/ConfigInterface.php
@@ -27,6 +27,14 @@ public function getUsername(): string;
     public function getPassword(): string;
 
 
+    /**
+     *
+     * Gets access key
+     *
+     * @return string $accessKey
+     */
+    public function getAccessKey(): string;
+
     /**
      *
      * Gets the storeId
diff --git a/src/Invoice/Article/Article.php b/src/Invoice/Article/Article.php
index 07a4252..e477772 100644
--- a/src/Invoice/Article/Article.php
+++ b/src/Invoice/Article/Article.php
@@ -123,6 +123,7 @@ public function toArray()
             'ArticleId'     => $this->articleId,
             'Description'   => $this->description,
             'Quantity'      => $this->quantity,
+            'UnitPrice'     => $this->unitPrice,
         ];
     }
 }