The Bucks will use the stretch provision to spread the balance of Hawes' $6.2 million salary this season over three years, sparing the franchise the full salary-cap hit this year.
Hawes, 29, was traded to Milwaukee in a February deal with Charlotte. Once Hawes clears waivers, he will become an unrestricted free agent.
Hawes has averaged 8.7 points and 5.7 rebounds in 10 NBA seasons, including stops with Sacramento, Philadelphia, Cleveland, the LA Clippers, Charlotte and Milwaukee.
The Bucks are now $2.5 million under the tax threshold with 13 guaranteed contracts.