diff --git a/htdocs/langs/en_US/products.lang b/htdocs/langs/en_US/products.lang
index af8f850a858..7181b24d39b 100644
--- a/htdocs/langs/en_US/products.lang
+++ b/htdocs/langs/en_US/products.lang
@@ -404,7 +404,8 @@ PMPValueShort=WAP
 mandatoryperiod=Mandatory periods
 mandatoryPeriodNeedTobeSet=Note: Period (start and end date) must be defined
 mandatoryPeriodNeedTobeSetMsgValidate=A service requires a start and end period
-mandatoryHelper=Check this if you want a message to the user when creating / validating an invoice, commercial proposal, sales order without entering a start and end date on lines with this service.<br>Note that the message is a warning and not a blocking error.
+mandatoryHelper=Check this if you want a message to the user when creating / validating an invoice, commercial proposal, sales order without entering a start and end date on lines with this service.
+mandatoryHelper2=Note that the message is a warning and not a blocking error.
 DefaultBOM=Default BOM
 DefaultBOMDesc=The default BOM recommended to use to manufacture this product. This field can be set only if nature of product is '%s'.
 Rank=Rank
diff --git a/htdocs/product/card.php b/htdocs/product/card.php
index 88c2acf96a7..6ea9c3f8848 100644
--- a/htdocs/product/card.php
+++ b/htdocs/product/card.php
@@ -1560,6 +1560,9 @@ if (is_object($objcanvas) && $objcanvas->displayCanvasExists($canvasdisplayactio
 				print '<input type="checkbox" id="mandatoryperiod" name="mandatoryperiod"'.($object->mandatory_period == 1 ? ' checked="checked"' : '').'>';
 				print '<label for="mandatoryperiod">';
 				$htmltooltip = $langs->trans("mandatoryHelper");
+				if (!getDolGlobalString('SERVICE_STRICT_MANDATORY_PERIOD')) {
+					$htmltooltip .= '<br>'.$langs->trans("mandatoryHelper2");
+				}
 				print $form->textwithpicto($langs->trans("mandatoryperiod"), $htmltooltip, 1, 0);
 				print '</label>';
 
@@ -2179,6 +2182,9 @@ if (is_object($objcanvas) && $objcanvas->displayCanvasExists($canvasdisplayactio
 					print '<input type="checkbox" id="mandatoryperiod" name="mandatoryperiod"'.($object->mandatory_period == 1 ? ' checked="checked"' : '').'>';
 					print '<label for="mandatoryperiod">';
 					$htmltooltip = $langs->trans("mandatoryHelper");
+					if (!getDolGlobalString('SERVICE_STRICT_MANDATORY_PERIOD')) {
+						$htmltooltip .= '<br>'.$langs->trans("mandatoryHelper2");
+					}
 					print $form->textwithpicto($langs->trans("mandatoryperiod"), $htmltooltip, 1, 0);
 					print '</label>';
 
@@ -2703,6 +2709,9 @@ if (is_object($objcanvas) && $objcanvas->displayCanvasExists($canvasdisplayactio
 						print ' &nbsp; &nbsp; &nbsp; ';
 					}
 					$htmltooltip = $langs->trans("mandatoryHelper");
+					if (!getDolGlobalString('SERVICE_STRICT_MANDATORY_PERIOD')) {
+						$htmltooltip .= '<br>'.$langs->trans("mandatoryHelper2");
+					}
 					print '<input type="checkbox" class="" name="mandatoryperiod"'.($object->mandatory_period == 1 ? ' checked="checked"' : '').' disabled>';
 					print $form->textwithpicto($langs->trans("mandatoryperiod"), $htmltooltip, 1, 0);