If the incident sounds familiar -- it should -- it's the same case that was recently rejected by the D.A.'s Office after the office claimed it was a civil matter ... so the promoter is doing just that.

According to new legal docs obtained by TMZ ... Sadaetirs Kent Smith, a club promoter, is now suing the rapper alleging he bailed on a performance back in September 2016 and never returned the amount he had been paid ... $16,500.

We broke the story ... the promoter went to cops in October 2016 and filed paperwork to get a felony warrant against 21 Savage for theft by deception, claiming he walked off with $17k for a show that never went down.

As for the $1 million figure ... Smith says the breach of contract caused severe emotional distress.