Does Policy Statement 8.0 require a broker to turn in every listing to the MLS within 1 business day of signing the listing?

No. MLSs have different local rules as to listing turn-in times. If a listing is taken and is not yet ready to be marketed/shown, longer timelines for turn in may apply in local markets. If a listing is marketed to the public, however, Policy Statement 8.0’s 1 business day turn-in timeline goes into effect.