GM last month said about 19,000 workers opted for one of the packages, which included 1,259 who had already retired and were eligible retroactively. Workers had a week to change their minds after taking an offer.
Most workers will be gone by July 1.
Nearly half those leaving -- about 8,500 -- are from Michigan factories. The Flint area alone is set to lose 1,800 workers.
GM extended the offers to all 74,000 United Auto Workers-represented employees in the U.S. as part of a plan to move out highly paid veterans and replace them with lower-wage new hires.