'Do' And 'does' are each forms of your current indefinite tense in the verb 'to carry out.' Which a single you will use will mostly rely upon the sentence's issue. Their usage is sort of equivalent, except for one occasion where You need to use 'do' and never 'does.' https://financefeeds.com/clearstream-to-serve-as-a-triparty-agent-for-euronext-clearing/