The Writers Guild of America (WGA) has a well-defined process for determining credits on projects produced under its jurisdiction. These productions are generally USA-controlled live-action film and TV projects, produced either by studios or major independent producers. In 1999, the WGA began furnishing credits directly to IMDb. The absence of the WGA indicator on earlier credits should not be construed as a sign of unofficial status, merely a sign of age.

In general, the credits determination process works as follows:
When the film is finished shooting, the producer sends a notice to the guild and the writers proposing the writing credits. If any writer disagrees with those credits, or if the proposed credits require mandatory arbitration (e.g., a producer or director sharing a writing credit), a WGA arbitration committee reads all drafts of the script and various supporting materials and determines the actual/official credits.

If there is no source material (novel, play, article, etc.) and the same writers receive credit for both the story and screenplay, the credit is "written by".

The "story by" credit is used when the basic narrative structure was originally written with intent to be used for a movie (as opposed to a short story) and the actual screenplay had different authors. A shared "story by" credit is the minimum awarded to the author of an original screenplay.

If there was previously existing source material but the writer creates a substantially new and different story from the source, then the "screen story" (or "television story") credit is used.

Finally, the "screenplay by" (or "teleplay by") credit is used to denote the screenplay (teleplay) authorship if the story credit had to be separated as above.

In rare cases, "adaptation by" can be awarded to a writer who shapes the script without qualifying for one of the above credits.

There are other specialized credits used for television programs such as documentaries and audience participation shows.
Within each of these categories, members of a writing team are joined by "&"; teams or writers working on separate drafts are joined by "and".

The IMDb will not accept uncredited writers for titles with WGA-determined credits.

The WGA is also on the world wide web. Their address is http://www.wga.org/