I was recently approached by a copywriter who was confused about the proper use of copyright. He explained that the client had hired him for work, then canceled the job part way through, paying him for work done to date.

Perhaps because the work was unfinished, and thinking
there may be some future use for it, the copywriter expressed that felt he should retain copyright, and was perplexed when the client got into a snit about it.

I understand the idea to save good work that never got
published, hoping to "recycle" it in future jobs. For
years I hung on to a two-inch think file of unused
concepts.

When a new job came along that required concepting, I'd leaf through the folder looking for something that
would "fit" the new challenge.

Alas, I never did find a perfect fit between an old
concept and a new job. And one day I realized I never
would. That's because every job is unique. Every product is unique, every audience is unique, every marketing objective is unique. The strongest concept would once again have to come from my head. I threw out the contents of the file and never looked back.

So the lesson learned is that if you can't even recycle a concept, you'll never be able to recycle copy, which is much more granular.

Therefore it makes no sense to try and retain copyright; if your work is "for hire," meaning that you're being paid to do the writing, you can't retain copyright anyway.

The United States Copyright Act gives the purchaser of the work sole copyright. To understand the difference, you, the copywriter, would retain copyright of a work you did not do for hire. For instance, no one is paying me to write this article. So I'm able to retain copyright, and market the article as I see fit.

One final important note about copywriters and copyrights. You do retain copyright until the work is paid in full. So use this fact to your advantage. Make sure your Fee Agreement points out that you will retain copyright until paid in full. It's a powerful way to use the work-for-hire copyright law to your advantage; I'm sure that having this clause in my own Fee Agreement has saved me some grief over the years.