You do if you’ve written licensed fiction based on a TV show, motion picture, computer game, stage play, comic book (or strip), radio serial or other dramatic work as long as you were paid for it and it has been published (or is about to be). The membership committee will determine, on a case-by-case basis, what qualifies as “other dramatic work” (for instance, a series of books based on a toy or doll).
It doesn’t matter whether you’ve written forty novels or one short story, whether it was published last week or thirty years ago, you qualify for membership as long as you were paid for your licensed work and it was published (or is about to be).
Fanfiction does not qualify.
Contact the IAMTW to ask how to join:
PO Box 8212
Calabasas, CA 91372
Email: tieinwriters AT gmail DOT com