diff --git a/htdocs/compta/facture/class/facture.class.php b/htdocs/compta/facture/class/facture.class.php
index d4c616d09ac26..4b5da68f8a293 100644
--- a/htdocs/compta/facture/class/facture.class.php
+++ b/htdocs/compta/facture/class/facture.class.php
@@ -358,7 +358,7 @@ function create($user,$notrigger=0,$forceduedate=0)
 		$sql.= ", ".($this->remise_absolue>0?$this->remise_absolue:'NULL');
 		$sql.= ", ".($this->remise_percent>0?$this->remise_percent:'NULL');
 		$sql.= ", '".$this->db->idate($this->date)."'";
-		$sql.= ", '".$this->db->idate($this->date_pointoftax)."'";
+		$sql.= ", ".(strval($this->date_pointoftax)!='' ? "'".$this->db->idate($this->date_pointoftax)."'" : 'null');
 		$sql.= ", ".($this->note_private?"'".$this->db->escape($this->note_private)."'":"null");
 		$sql.= ", ".($this->note_public?"'".$this->db->escape($this->note_public)."'":"null");
 		$sql.= ", ".($this->ref_client?"'".$this->db->escape($this->ref_client)."'":"null");
diff --git a/htdocs/install/mysql/migration/3.9.0-4.0.0.sql b/htdocs/install/mysql/migration/3.9.0-4.0.0.sql
index c20ef305c3974..935f8a04917b2 100644
--- a/htdocs/install/mysql/migration/3.9.0-4.0.0.sql
+++ b/htdocs/install/mysql/migration/3.9.0-4.0.0.sql
@@ -111,7 +111,7 @@ ALTER TABLE llx_cronjob ADD COLUMN test varchar(255) DEFAULT '1';
 
 ALTER TABLE llx_facture ADD INDEX idx_facture_fk_statut (fk_statut);
 
-ALTER TABLE llx_facture ADD COLUMN date_pointoftax date;
+ALTER TABLE llx_facture ADD COLUMN date_pointoftax date DEFAULT NULL;
 
 UPDATE llx_projet as p set p.opp_percent = (SELECT percent FROM llx_c_lead_status as cls WHERE cls.rowid = p.fk_opp_status)  WHERE p.opp_percent IS NULL AND p.fk_opp_status IS NOT NULL;
  
@@ -506,4 +506,4 @@ CREATE TABLE llx_oauth_state (
     entity integer
 )ENGINE=InnoDB;
 
-ALTER TABLE llx_import_model MODIFY COLUMN type varchar(50);
\ No newline at end of file
+ALTER TABLE llx_import_model MODIFY COLUMN type varchar(50);
diff --git a/htdocs/install/mysql/tables/llx_facture.sql b/htdocs/install/mysql/tables/llx_facture.sql
index b8e97f4dc1e7c..f62d845295305 100644
--- a/htdocs/install/mysql/tables/llx_facture.sql
+++ b/htdocs/install/mysql/tables/llx_facture.sql
@@ -38,7 +38,7 @@ create table llx_facture
   fk_soc				integer            NOT NULL,
   datec					datetime,								-- date de creation de la facture
   datef					date,									-- date invoice
-  date_pointoftax		date,									-- date point of tax (for GB)
+  date_pointoftax		date DEFAULT NULL,									-- date point of tax (for GB)
   date_valid			date,									-- date validation
   tms					timestamp,								-- date creation/modification
   paye					smallint DEFAULT 0 NOT NULL,