diff --git a/htdocs/compta/facture/class/api_invoices.class.php b/htdocs/compta/facture/class/api_invoices.class.php
index e68966f4663..af69fd79008 100644
--- a/htdocs/compta/facture/class/api_invoices.class.php
+++ b/htdocs/compta/facture/class/api_invoices.class.php
@@ -1,5 +1,6 @@
 <?php
 /* Copyright (C) 2015   Jean-François Ferry     <jfefe@aternatik.fr>
+/* Copyright (C) 2020   Thibault FOUCART     	<support@ptibogxiv.net>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -63,11 +64,66 @@ class Invoices extends DolibarrApi
      */
 	public function get($id, $contact_list = 1)
 	{
+        return $this->_fetch($id, '', '', '', $contact_list);
+	}
+
+    /**
+     * Get properties of an invoice object by ref
+     *
+     * Return an array with invoice informations
+     *
+     * @param       string		$ref			Ref of object
+     * @param       int         $contact_list  0: Returned array of contacts/addresses contains all properties, 1: Return array contains just id
+     * @return 	array|mixed data without useless information
+     *
+     * @url GET    ref/{ref}
+     *
+     * @throws 	RestException
+     */
+    public function getByRef($ref, $contact_list = 1)
+    {
+        return $this->_fetch('', $ref, '', '', $contact_list);
+    }
+
+    /**
+     * Get properties of an invoice object by ref_ext
+     *
+     * Return an array with invoice informations
+     *
+     * @param       string		$ref_ext			External reference of object
+     * @param       int         $contact_list  0: Returned array of contacts/addresses contains all properties, 1: Return array contains just id
+     * @return 	array|mixed data without useless information
+     *
+     * @url GET    ref_ext/{ref_ext}
+     *
+     * @throws 	RestException
+     */
+    public function getByRefExt($ref_ext, $contact_list = 1)
+    {
+        return $this->_fetch('', '', $ref_ext, '', $contact_list);
+    }
+
+    /**
+     * Get properties of an order object
+     *
+     * Return an array with order informations
+     *
+     * @param       int         $id            ID of order
+	 * @param		string		$ref			Ref of object
+	 * @param		string		$ref_ext		External reference of object
+	 * @param		string		$ref_int		Internal reference of other objec
+     * @param       int         $contact_list  0: Returned array of contacts/addresses contains all properties, 1: Return array contains just id
+     * @return 	array|mixed data without useless information
+     *
+     * @throws 	RestException
+     */
+    private function _fetch($id, $ref = '', $ref_ext = '', $ref_int = '', $contact_list = 1)
+    {
 		if (!DolibarrApiAccess::$user->rights->facture->lire) {
 			throw new RestException(401);
 		}
 
-		$result = $this->invoice->fetch($id);
+		$result = $this->invoice->fetch($id, $ref, $ref_ext, $ref_int);
 		if (!$result) {
 			throw new RestException(404, 'Invoice not found');
 		}
@@ -87,7 +143,7 @@ class Invoices extends DolibarrApi
 
 		$this->invoice->fetchObjectLinked();
 		return $this->_cleanObjectDatas($this->invoice);
-	}
+    }
 
     /**
      * List invoices
@@ -424,7 +480,7 @@ class Invoices extends DolibarrApi
 	 * @url	DELETE {id}/contact/{rowid}
 	 *
 	 * @return array
-	 *
+  	 *
      * @throws RestException 401
      * @throws RestException 404
      * @throws RestException 500
@@ -592,6 +648,7 @@ class Invoices extends DolibarrApi
      *
      * @return int
      *
+     * @throws RestException 304
      * @throws RestException 401
      * @throws RestException 404
      * @throws RestException 400
@@ -1098,6 +1155,7 @@ class Invoices extends DolibarrApi
      * @url     POST {id}/usediscount/{discountid}
      *
      * @return int
+	 *
      * @throws RestException 400
      * @throws RestException 401
      * @throws RestException 404
@@ -1144,6 +1202,7 @@ class Invoices extends DolibarrApi
      * @url     POST {id}/usecreditnote/{discountid}
      *
      * @return int
+     *
      * @throws RestException 400
      * @throws RestException 401
      * @throws RestException 404
@@ -1189,7 +1248,7 @@ class Invoices extends DolibarrApi
      * @url     GET {id}/payments
      *
      * @return array
-     *
+	 *
      * @throws RestException 400
      * @throws RestException 401
      * @throws RestException 404
@@ -1239,6 +1298,7 @@ class Invoices extends DolibarrApi
      * @url     POST {id}/payments
      *
      * @return int  Payment ID
+	 *
      * @throws RestException 400
      * @throws RestException 401
      * @throws RestException 404
@@ -1358,6 +1418,7 @@ class Invoices extends DolibarrApi
      * @url     POST /paymentsdistributed
      *
      * @return int  Payment ID
+	 *
      * @throws RestException 400
      * @throws RestException 401
      * @throws RestException 403