Sometimes you want to register a custom taxonomy in WordPress and retain the editing UI, but not have your post editing screen littered with a tonne of meta boxes. In my instance, the values assigned to a post are set through an alternative UI or as hidden values.

Fortunately, you can keep the editing UI for custom taxonomies and specify you don't want a metabox with a simple argument.

In your taxonomy options, all you need to provide is the value meta_box_cb and set it to false

$args = array(   'hierarchical' => false,   'show_ui'      => true,   'query_var'    => true,   'meta_box_cb'  => false );  register_taxonomy( 'mytax', 'post', $args );

It is really that simple.