If the line from the idea to you isn't clean, nobody can buy it.

Chain of title is the paper trail that proves who owns the story. A producer's lawyer asks for it before any money moves, and most writers hear the phrase for the first time when a deal is already slowing down.

It covers more than you'd think. Your WGA registration and your copyright filing. Any release you signed with a co-writer, including the friend who spent a weekend helping you break act two and never got paid. The rights to the book, the article, or the real person the story came from. If a lawyer can't draw a clean line from the idea to you, the script can't be bought. Not won't. Can't.

Erin Brockovich is the clean version of this. Susannah Grant wrote it and Steven Soderbergh directed it, but before either of them started, somebody had to sit down with the real Erin Brockovich and buy the right to tell her story. A living person's life isn't public domain. No signature, no movie, however good the script is.

There's also a smaller version. You wrote a spec four years ago with someone you don't speak to now. You never put anything in writing because you were friends. Today a producer wants it and your friend owns half of something nobody ever defined. That would've been a lot cheaper to settle when you started the project.

So write the boring documents while everyone still likes each other. A one page co-writer agreement. A signed release for the interview. A receipt for the option. When somebody questions what you own, and somebody will, signed agreements end it faster than a conversation does. Paper doesn't argue. It just sits there being the authority.