diff --git a/htdocs/compta/facture/class/facture.class.php b/htdocs/compta/facture/class/facture.class.php
index 81bf47715e68a..fb92a3b69e163 100644
--- a/htdocs/compta/facture/class/facture.class.php
+++ b/htdocs/compta/facture/class/facture.class.php
@@ -1406,75 +1406,6 @@ function delete($rowid=0, $notrigger=0, $idwarehouse=-1)
 		}
 	}
 
-
-	/**
-	 *	Renvoi une date limite de reglement de facture en fonction des
-	 *	conditions de reglements de la facture et date de facturation
-	 *
-	 *	@param      string	$cond_reglement   	Condition of payment (code or id) to use. If 0, we use current condition.
-	 *	@return     date     			       	Date limite de reglement si ok, <0 si ko
-	 */
-	function calculate_date_lim_reglement($cond_reglement=0)
-	{
-		if (! $cond_reglement) $cond_reglement=$this->cond_reglement_code;
-		if (! $cond_reglement) $cond_reglement=$this->cond_reglement_id;
-
-		$cdr_nbjour=0; $cdr_fdm=0; $cdr_decalage=0;
-
-		$sqltemp = 'SELECT c.fdm,c.nbjour,c.decalage';
-		$sqltemp.= ' FROM '.MAIN_DB_PREFIX.'c_payment_term as c';
-		if (is_numeric($cond_reglement)) $sqltemp.= " WHERE c.rowid=".$cond_reglement;
-		else $sqltemp.= " WHERE c.code='".$this->db->escape($cond_reglement)."'";
-
-		dol_syslog(get_class($this).'::calculate_date_lim_reglement sql='.$sqltemp);
-		$resqltemp=$this->db->query($sqltemp);
-		if ($resqltemp)
-		{
-			if ($this->db->num_rows($resqltemp))
-			{
-				$obj = $this->db->fetch_object($resqltemp);
-				$cdr_nbjour = $obj->nbjour;
-				$cdr_fdm = $obj->fdm;
-				$cdr_decalage = $obj->decalage;
-			}
-		}
-		else
-		{
-			$this->error=$this->db->error();
-			return -1;
-		}
-		$this->db->free($resqltemp);
-
-		/* Definition de la date limite */
-
-		// 1 : ajout du nombre de jours
-		$datelim = $this->date + ($cdr_nbjour * 3600 * 24);
-
-		// 2 : application de la regle "fin de mois"
-		if ($cdr_fdm)
-		{
-			$mois=date('m', $datelim);
-			$annee=date('Y', $datelim);
-			if ($mois == 12)
-			{
-				$mois = 1;
-				$annee += 1;
-			}
-			else
-			{
-				$mois += 1;
-			}
-			// On se deplace au debut du mois suivant, et on retire un jour
-			$datelim=dol_mktime(12,0,0,$mois,1,$annee);
-			$datelim -= (3600 * 24);
-		}
-
-		// 3 : application du decalage
-		$datelim += ($cdr_decalage * 3600 * 24);
-
-		return $datelim;
-	}
-
 	/**
 	 *  Tag la facture comme paye completement (si close_code non renseigne) => this->fk_statut=2, this->paye=1
 	 *  ou partiellement (si close_code renseigne) + appel trigger BILL_PAYED => this->fk_statut=2, this->paye stay 0
diff --git a/htdocs/core/class/commoninvoice.class.php b/htdocs/core/class/commoninvoice.class.php
index 80d719decaea5..6d657f0c36caa 100644
--- a/htdocs/core/class/commoninvoice.class.php
+++ b/htdocs/core/class/commoninvoice.class.php
@@ -288,6 +288,74 @@ function LibStatut($paye,$status,$mode=0,$alreadypaid=-1,$type=0)
 			}
 		}
 	}
+
+	/**
+	 *	Renvoi une date limite de reglement de facture en fonction des
+	 *	conditions de reglements de la facture et date de facturation
+	 *
+	 *	@param      string	$cond_reglement   	Condition of payment (code or id) to use. If 0, we use current condition.
+	 *	@return     date     			       	Date limite de reglement si ok, <0 si ko
+	 */
+	function calculate_date_lim_reglement($cond_reglement=0)
+	{
+		if (! $cond_reglement) $cond_reglement=$this->cond_reglement_code;
+		if (! $cond_reglement) $cond_reglement=$this->cond_reglement_id;
+
+		$cdr_nbjour=0; $cdr_fdm=0; $cdr_decalage=0;
+
+		$sqltemp = 'SELECT c.fdm,c.nbjour,c.decalage';
+		$sqltemp.= ' FROM '.MAIN_DB_PREFIX.'c_payment_term as c';
+		if (is_numeric($cond_reglement)) $sqltemp.= " WHERE c.rowid=".$cond_reglement;
+		else $sqltemp.= " WHERE c.code='".$this->db->escape($cond_reglement)."'";
+
+		dol_syslog(get_class($this).'::calculate_date_lim_reglement sql='.$sqltemp);
+		$resqltemp=$this->db->query($sqltemp);
+		if ($resqltemp)
+		{
+			if ($this->db->num_rows($resqltemp))
+			{
+				$obj = $this->db->fetch_object($resqltemp);
+				$cdr_nbjour = $obj->nbjour;
+				$cdr_fdm = $obj->fdm;
+				$cdr_decalage = $obj->decalage;
+			}
+		}
+		else
+		{
+			$this->error=$this->db->error();
+			return -1;
+		}
+		$this->db->free($resqltemp);
+
+		/* Definition de la date limite */
+
+		// 1 : ajout du nombre de jours
+		$datelim = $this->date + ($cdr_nbjour * 3600 * 24);
+
+		// 2 : application de la regle "fin de mois"
+		if ($cdr_fdm)
+		{
+			$mois=date('m', $datelim);
+			$annee=date('Y', $datelim);
+			if ($mois == 12)
+			{
+				$mois = 1;
+				$annee += 1;
+			}
+			else
+			{
+				$mois += 1;
+			}
+			// On se deplace au debut du mois suivant, et on retire un jour
+			$datelim=dol_mktime(12,0,0,$mois,1,$annee);
+			$datelim -= (3600 * 24);
+		}
+
+		// 3 : application du decalage
+		$datelim += ($cdr_decalage * 3600 * 24);
+
+		return $datelim;
+	}
 }
 
 /**
diff --git a/htdocs/fourn/facture/fiche.php b/htdocs/fourn/facture/fiche.php
index 92c8be3469cfa..46932f5de970e 100644
--- a/htdocs/fourn/facture/fiche.php
+++ b/htdocs/fourn/facture/fiche.php
@@ -300,6 +300,9 @@
 		$object->cond_reglement_id = GETPOST('cond_reglement_id');
         $object->mode_reglement_id = GETPOST('mode_reglement_id');
         $object->fk_project    = ($tmpproject > 0) ? $tmpproject : null;
+		
+		// Auto calculation of date due if not filled by user
+		if(empty($object->date_echeance)) $object->date_echeance = $object->calculate_date_lim_reglement();
 
         // If creation from another object of another module
         if ($_POST['origin'] && $_POST['originid'])