diff --git a/course/moodleform_mod.php b/course/moodleform_mod.php
index f6017efd7e3..d9156d8d9f1 100644
--- a/course/moodleform_mod.php
+++ b/course/moodleform_mod.php
@@ -255,6 +255,7 @@ class moodleform_mod extends moodleform {
 
         $mform->addElement('modvisible', 'visible', get_string('visible'));
         $mform->addElement('text', 'cmidnumber', get_string('idnumber'));
+        $mform->setHelpButton('cmidnumber', array('cmidnumber', get_string('idnumber')), true);
 
         if ($this->_features->gradecat) {
             $categories = grade_get_categories_menu($COURSE->id, $outcomesused);
diff --git a/lang/en_utf8/help/cmidnumber.html b/lang/en_utf8/help/cmidnumber.html
new file mode 100644
index 00000000000..ae87d6d3a38
--- /dev/null
+++ b/lang/en_utf8/help/cmidnumber.html
@@ -0,0 +1,5 @@
+<h1>ID number</h1>
+<p>Setting an ID number provides a way of identifying the activity for grade calculation purposes. 
+If the activity is not included in any grade calculation then the ID number field can be left blank.</p>
+<p> The ID number can also be set on the edit grade calculation page in the gradebook, though it can 
+only be edited on the update activity page.</p>