'Add new tag' button missing on taxonomy field

Symptom: A taxonomy field with Create Terms enabled is rendered on a front-end form, but the “Add new tag” button/icon doesn’t appear for some users — even though the field itself is showing fine.

Cause: ACF only exposes the inline term-creation control to users who hold the manage_terms capability for the relevant taxonomy. Logged-in users without that cap (and logged-out visitors) see the field but not the add button — by design.

The exact capability name depends on the taxonomy. Each taxonomy maps manage_terms to its own underlying cap, which you can inspect via get_taxonomy():

get_taxonomy( 'category' )->cap->manage_terms;
// 'manage_categories'

get_taxonomy( 'post_tag' )->cap->manage_terms;
// 'manage_post_tags'

Custom taxonomies registered with register_taxonomy() either inherit defaults or define their own caps via the capabilities argument — check what your taxonomy is actually mapped to before granting anything.

Fix: Grant the relevant manage_terms capability to the user role that needs to add terms from the front-end form. The User Role Editor plugin is the easiest way to manage this through the admin UI. If you’d rather do it in code:

add_action( 'init', function () {
    $role = get_role( 'subscriber' );

    if ( $role && ! $role->has_cap( 'manage_categories' ) ) {
        $role->add_cap( 'manage_categories' );
    }
} );

Be deliberate about which role you grant this to — manage_terms lets users create, edit, and delete terms in that taxonomy site-wide, not just via the front-end form.