diff --git a/mail.php b/mail.php
index c0f3251..3a0440f 100755
--- a/mail.php
+++ b/mail.php
@@ -2,8 +2,10 @@
 require_once "Mail.php";
 include('Mail/mime.php');
 include 'config.php';
+include_once 'User.php';
+use \User as User;
 
-function send_mail(string $email, object $smtp, object $message) {
+function send_mail(string $email, object $smtp, object $message, User $user = null) {
     include 'config.php';
 
     $crlf = "\r\n";
@@ -41,6 +43,9 @@
     // Setting the body of the email
     $mime->setTXTBody($message->text);
     $mime->setHTMLBody($message->html);
+    if ($user && $user->invoice) {
+        $mime->addAttachment ( $user->invoice , 'application/pdf' , $SERVICE_ACRONYM."-invoice.pdf" , false, "base64" );
+    }
 
     $body = $mime->get();
     $headers = $mime->headers($headers);