All sending domains need to be listed, but subdomains do not as they will be covered by the base domain.
For example, if you have 3 sending domains like mail.example.com, marketing.example.com and example.com, you only need to list example.com in your request. You are free to list each subdomain if you like, but it is not necessary—and if you do list them, there will be a charge.
But if you are also sending from example.co.uk, then that should be listed because it’s a different domain.