As soon as you have completed your screenplay, you should consider copyrighting it to protect your intellectual property. While copyright protection is automatic once you have created an original work, registering your copyright with the United States Copyright Office can provide additional legal benefits. For example, if you need to sue for copyright infringement, you will need to have registered your copyright. In addition, registering your copyright can also make it easier to prove ownership of the work in question.
To register your screenplay with the Copyright Office, you will need to submit a completed copyright application, a copy of your screenplay, and the appropriate fee. You can file your application online or by mail. It is generally a good idea to register your copyright as soon as possible after completing your screenplay to ensure that you are fully protected.