register_taxonomy problem with non hierarchical type

I have successfull adding/register a couple of new taxonomy that been used in the custom post type editor page.

Where I need to add some sort of type(such as ‘Released Year’-which need only a 1 year been determined). However from the non hierarchical taxonomy, it allow user to add more than 1 year.

Is there’s any WP built-in that can overcame this problem or does I need to code the script itself.

Thanks in advance