Dealers must register to participate in the cash for guzzlers program passed Thursday by the Senate and expected to receive President Barack Obamas signature.
The legislation says the government must establish a procedure for registering dealers within 30 days of Obamas signing.
But the program can apply to new vehicles purchased or leased between July 1 and Nov. 1, 2009, so dealers and consumers can start considering participation now.
The legislation, designed to help lift U.S. light-vehicle sales from 27-year lows, provides vouchers of $3,500 to $4,500 to consumers who trade in their rides for new vehicles that are more fuel-efficient. Congress allocated $1 billion to fund the program.
Here are the program details, as outlined in the bill approved this week by the House and Senate.