People who trade in their car to buy a new one would see a sales tax cut phased in more quickly under bills sent to Gov. Rick Snyder.
Buyers can subtract the value of their trade-in from the purchase price of a new vehicle for tax purposes under a 2013 law.
The legislation finalized by the Republican-led Senate Thursday would accelerate the phase-in of the tax break to 2029 - 10 years sooner.
The bills' supporters say the law helped boost auto sales and buyers deserve a fully phased-in tax reduction earlier.
Opponents such as school and local government advocates worry about lost tax revenue.
It is unclear if Snyder will sign the legislation. A spokesman says he will make a decision after reviewing the bills.