Do you have to pay for cot code?

Excuse me, I'm a bit confused about something I came across. I noticed a mention of "cot code" and I'm wondering, is there a fee associated with it? Do you have to pay for cot code in order to use it or access it? Could you clarify the situation for me, please? I'm trying to understand if there's any cost involved in obtaining or utilizing this cot code. Thank you for your help!