diff --git a/htdocs/compta/facture/card.php b/htdocs/compta/facture/card.php
index 2f1941ff836..3363548095f 100644
--- a/htdocs/compta/facture/card.php
+++ b/htdocs/compta/facture/card.php
@@ -297,31 +297,32 @@ if (empty($reshook))
 
 			// Also negative lines should not be allowed on 'non Credit notes' invoices. A test is done when adding or updating lines but we must
 			// do it again in validation to avoid cases where invoice is created from another object that allow negative lines.
-			// Note that we can accept the negative line if sum with other lines with same vat is positivie: Because all the lines will be merged together
+			// Note that we can accept the negative line if sum with other lines with same vat makes total positive: Because all the lines will be merged together
 			// when converted into 'available credit' and we will get a positive available credit line.
 			// Note: Other solution if you want to add a negative line on invoice, is to create a discount for customer and consumme it (but this is possible on standard invoice only).
-			$array_of_pu_ht_per_vat_rate = array();
-			$array_of_pu_ht_devise_per_vat_rate = array();
+			$array_of_total_ht_per_vat_rate = array();
+			$array_of_total_ht_devise_per_vat_rate = array();
 			foreach($object->lines as $line) {
-				if (empty($array_of_pu_ht_per_vat_rate[$line->tva_tx.'_'.$line->vat_src_code])) $array_of_pu_ht_per_vat_rate[$line->tva_tx.'_'.$line->vat_src_code] = 0;
-				if (empty($array_of_pu_ht_devise_per_vat_rate[$line->tva_tx.'_'.$line->vat_src_code])) $array_of_pu_ht_devise_per_vat_rate[$line->tva_tx.'_'.$line->vat_src_code] = 0;
-				$array_of_pu_ht_per_vat_rate[$line->tva_tx.'_'.$line->vat_src_code] += $line->subprice;
-				$array_of_pu_ht_devise_per_vat_rate[$line->tva_tx.'_'.$line->vat_src_code] += $line->multicurrency_subprice;
+				if (empty($array_of_total_ht_per_vat_rate[$line->tva_tx.'_'.$line->vat_src_code])) $array_of_total_ht_per_vat_rate[$line->tva_tx.'_'.$line->vat_src_code] = 0;
+				if (empty($array_of_total_ht_devise_per_vat_rate[$line->tva_tx.'_'.$line->vat_src_code])) $array_of_total_ht_devise_per_vat_rate[$line->tva_tx.'_'.$line->vat_src_code] = 0;
+				$array_of_total_ht_per_vat_rate[$line->tva_tx.'_'.$line->vat_src_code] += $line->total_ht;
+				$array_of_total_ht_devise_per_vat_rate[$line->tva_tx.'_'.$line->vat_src_code] += $line->multicurrency_subprice;
 			}
-			//var_dump($array_of_pu_ht_per_vat_rate);exit;
-			foreach($array_of_pu_ht_per_vat_rate as $vatrate => $tmpvalue)
-			{
-				$pu_ht = $array_of_pu_ht_per_vat_rate[$vatrate];
-				$pu_ht_devise = $array_of_pu_ht_devise_per_vat_rate[$vatrate];
 
-				if (($pu_ht < 0 || $pu_ht_devise < 0) && empty($conf->global->FACTURE_ENABLE_NEGATIVE_LINES))
+			//var_dump($array_of_total_ht_per_vat_rate);exit;
+			foreach($array_of_total_ht_per_vat_rate as $vatrate => $tmpvalue)
+			{
+				$tmp_total_ht = $array_of_total_ht_per_vat_rate[$vatrate];
+				$tmp_total_ht_devise = $array_of_total_ht_devise_per_vat_rate[$vatrate];
+
+				if (($tmp_total_ht < 0 || $tmp_total_ht_devise < 0) && empty($conf->global->FACTURE_ENABLE_NEGATIVE_LINES))
 				{
 					$langs->load("errors");
 					if ($object->type == $object::TYPE_DEPOSIT) {
 						// Using negative lines on deposit lead to headach and blocking problems when you want to consume them.
 						setEventMessages($langs->trans("ErrorLinesCantBeNegativeOnDeposits"), null, 'errors');
 					} else {
-						setEventMessages($langs->trans("ErrorFieldCantBeNegativeOnInvoice", $langs->transnoentitiesnoconv("UnitPriceHT"), $langs->transnoentitiesnoconv("CustomerAbsoluteDiscountShort")), null, 'errors');
+						setEventMessages($langs->trans("ErrorLinesCantBeNegativeForOneVATRate"), null, 'errors');
 					}
 					$error++;
 					$action = '';
@@ -5080,7 +5081,7 @@ elseif ($id > 0 || !empty($ref))
 			// Reverse back money or convert to reduction
 			if ($object->type == Facture::TYPE_CREDIT_NOTE || $object->type == Facture::TYPE_DEPOSIT || $object->type == Facture::TYPE_STANDARD || $object->type == Facture::TYPE_SITUATION) {
 				// For credit note only
-				if ($object->type == Facture::TYPE_CREDIT_NOTE && $object->statut == 1 && $object->paye == 0 && $usercanissuepayment)
+				if ($object->type == Facture::TYPE_CREDIT_NOTE && $object->statut == Facture::STATUS_VALIDATED && $object->paye == 0 && $usercanissuepayment)
 				{
 					if ($resteapayer == 0)
 					{
@@ -5093,12 +5094,12 @@ elseif ($id > 0 || !empty($ref))
 				}
 
 				// For standard invoice with excess received
-				if (($object->type == Facture::TYPE_STANDARD || $object->type == Facture::TYPE_SITUATION) && empty($object->paye) && $resteapayer < 0 && $usercancreate && empty($discount->id))
+				if (($object->type == Facture::TYPE_STANDARD || $object->type == Facture::TYPE_SITUATION) && $object->statut == Facture::STATUS_VALIDATED && empty($object->paye) && $resteapayer < 0 && $usercancreate && empty($discount->id))
 				{
 					print '<a class="butAction'.($conf->use_javascript_ajax ? ' reposition' : '').'" href="'.$_SERVER["PHP_SELF"].'?facid='.$object->id.'&amp;action=converttoreduc">'.$langs->trans('ConvertExcessReceivedToReduc').'</a>';
 				}
 				// For credit note
-				if ($object->type == Facture::TYPE_CREDIT_NOTE && $object->statut == 1 && $object->paye == 0 && $usercancreate
+				if ($object->type == Facture::TYPE_CREDIT_NOTE && $object->statut == Facture::STATUS_VALIDATED && $object->paye == 0 && $usercancreate
 					&& (! empty($conf->global->INVOICE_ALLOW_REUSE_OF_CREDIT_WHEN_PARTIALLY_REFUNDED) || $object->getSommePaiement() == 0)
 					) {
 					print '<a class="butAction'.($conf->use_javascript_ajax ? ' reposition' : '').'" href="'.$_SERVER["PHP_SELF"].'?facid='.$object->id.'&amp;action=converttoreduc" title="'.dol_escape_htmltag($langs->trans("ConfirmConvertToReduc2")).'">'.$langs->trans('ConvertToReduc').'</a>';
@@ -5111,7 +5112,7 @@ elseif ($id > 0 || !empty($ref))
 			}
 
 			// Classify paid
-			if (($object->statut == 1 && $object->paye == 0 && $usercanissuepayment && (($object->type != Facture::TYPE_CREDIT_NOTE && $object->type != Facture::TYPE_DEPOSIT && $resteapayer <= 0) || ($object->type == Facture::TYPE_CREDIT_NOTE && $resteapayer >= 0)))
+			if (($object->statut == Facture::STATUS_VALIDATED && $object->paye == 0 && $usercanissuepayment && (($object->type != Facture::TYPE_CREDIT_NOTE && $object->type != Facture::TYPE_DEPOSIT && $resteapayer <= 0) || ($object->type == Facture::TYPE_CREDIT_NOTE && $resteapayer >= 0)))
 				|| ($object->type == Facture::TYPE_DEPOSIT && $object->paye == 0 && $object->total_ttc > 0 && $resteapayer == 0 && $usercanissuepayment && empty($discount->id))
 			)
 			{
@@ -5120,7 +5121,7 @@ elseif ($id > 0 || !empty($ref))
 
 			// Classify 'closed not completely paid' (possible si validee et pas encore classee payee)
 
-			if ($object->statut == 1 && $object->paye == 0 && $resteapayer > 0 && $usercanissuepayment)
+			if ($object->statut == Facture::STATUS_VALIDATED && $object->paye == 0 && $resteapayer > 0 && $usercanissuepayment)
 			{
 				if ($totalpaye > 0 || $totalcreditnotes > 0)
 				{
diff --git a/htdocs/langs/en_US/errors.lang b/htdocs/langs/en_US/errors.lang
index 525131b2a61..c5b61e50ed6 100644
--- a/htdocs/langs/en_US/errors.lang
+++ b/htdocs/langs/en_US/errors.lang
@@ -117,7 +117,8 @@ ErrorLoginDoesNotExists=User with login <b>%s</b> could not be found.
 ErrorLoginHasNoEmail=This user has no email address. Process aborted.
 ErrorBadValueForCode=Bad value for security code. Try again with new value...
 ErrorBothFieldCantBeNegative=Fields %s and %s can't be both negative
-ErrorFieldCantBeNegativeOnInvoice=Field <strong>%s</strong> cannot be negative on this type of invoice. If you need to add a discount line, just create the discount first (from field '%s' in thirdparty card) and apply it to the invoice. You can also ask your admin to set option FACTURE_ENABLE_NEGATIVE_LINES to 1 to allow the old behaviour.
+ErrorFieldCantBeNegativeOnInvoice=Field <strong>%s</strong> cannot be negative on this type of invoice. If you need to add a discount line, just create the discount first (from field '%s' in thirdparty card) and apply it to the invoice.
+ErrorLinesCantBeNegativeForOneVATRate=Total of lines can't be negative for a given VAT rate.
 ErrorLinesCantBeNegativeOnDeposits=Lines can't be negative in a deposit. You will face problems when you will need to consume the deposit in final invoice if you do so.
 ErrorQtyForCustomerInvoiceCantBeNegative=Quantity for line into customer invoices can't be negative
 ErrorWebServerUserHasNotPermission=User account <b>%s</b> used to execute web server has no permission for that