How to turn off wordpress update notification

For all the WordPress users, it is really annoying when WordPress update notice is displayed on the dashboard if there are any upgrade available for the installed WordPress version as shown in the figure below. The notice will not clear until the WordPress is upgraded to latest version. Similarly the update notice for installed plugins & themes is displayed on the WordPress dashboard, plugins & themes pages. Actually it is good to know that updates are available but administrators who maintain multiple installations of WordPress on behalf of other people (eg. clients) may not want theme update notifications to be shown to the users of these installations, then disabling such notifications becomes necessary. In this article, I will show how to disable update notifications for core WordPress as well as for plugins and themes.

1. To Disable Update WordPress nag :

Insert the following code to the functions.php file of your active theme. It will remove the WordPress update nag e.g. WordPress 3.9.1 is available! Please update now, from the all users dashboard, admin dashboard & from Updates page as well.

add_action('after_setup_theme','remove_core_updates');
function remove_core_updates()
{
 if(! current_user_can('update_core')){return;}
 add_action('init', create_function('$a',"remove_action( 'init', 'wp_version_check' );"),2);
 add_filter('pre_option_update_core','__return_null');
 add_filter('pre_site_transient_update_core','__return_null');
}

2. To Disable Plugin Update Notifications :

Insert the following code to the functions.php file of your active theme. It will remove the update notifications of all the installed plugins.

remove_action('load-update-core.php','wp_update_plugins');
add_filter('pre_site_transient_update_plugins','__return_null');

3. To Disable all the Nags & Notifications :

Insert the following code the functions.php file of your active theme. This code disables all the updates notifications regarding plugins, themes & WordPress completely.

function remove_core_updates(){
global $wp_version;return(object) array('last_checked'=> time(),'version_checked'=> $wp_version,);
}
add_filter('pre_site_transient_update_core','remove_core_updates');
add_filter('pre_site_transient_update_plugins','remove_core_updates');
add_filter('pre_site_transient_update_themes','remove_core_updates');

Apart form these codes there are some WordPress plugins available to Disable WordPress Update Notifications & Nags :
If you install & activate these plugins, you will have to keep yourself updated with the latest version of your active WordPress, plugins & themes so that your blog or website wont be susceptible to security vulnerabilities or performance issues. Just deactivate the plugin for short period of time & update yourself.