The Writers Guild of America (WGA) credit system for motion pictures and television programs covers all works under the jurisdiction of the Writers Guild of America, East (WGAE) and the Writers Guild of America, West (WGAW). The WGA, originally the Screen Writers Guild, has since 1941 been the final arbiter of who receives credit for writing a theatrical, television or new media motion picture written under its jurisdiction.
The system has rules on how writers should be billed during the credits. A variety of credit forms can be given to indicate technicalities such as whether a writer contributed to the original source material, the chronological order of contributors working on different drafts, or whether there were writing teams. Since its inception, writers must have contributed at least 33 percent of a final script to receive credit, and only a certain number of writers can receive credit.
A determination process for screen credits first sees the production company submit proposed credits; about a third of these are challenged and taken to arbitration. This process asks all writing parties involved to provide evidence and supporting statements to help determine how much of the final product was each writer's work. However, several of the WGA's arbitration decisions have been criticized by WGA members, including how the process handles existing source material that is adapted to the screen, or whether writers of a particular draft should still be credited if subsequent drafts completely removed their contributions.