Does a clothing line logo need to be trademarked or copyrighted?

Answer 1

The creator has copyright on a logo unless they sell it or give it away.

If you mean "Do I need to pay to register my logo"... not necessarily, as long as you understand that if someone else steals it you would have no legal recourse... unless you can prove beyond a shadow of a doubt that you created the logo and were using the logo first, and are defending it when others try to steal it.

Trademarking the artwork means it's registered in a database that others can search when coming up with their own logo.

You can bet that McD's has trademarked their Big M logo a long time ago. And there's a good reason you don't see that big yellow M on any product belonging to another company.

There's also a reason that you never see the word "Kleenex" in a novel. If a writer wants to use that word they would require permission from the Kimberly-Clark Corporation. If permission is not granted and the writer uses the word anyways, Kimberly-Clark Corporation is obligated to sue the publisher. If they don't, Kimberly-Clark Corporation is allowing their trademarked name, "Kleenex" to fall into public domain usage. They don't want "Kleenex" to become the generic word for facial tissues.

So your logo clothing line should be unique, and trademarked, and should identify the company specifically.