 It's 520. It's time to get to a money update. A nationwide car dealer will now let customers take advantage of federal tax incentives for certain vehicles. Carvana now lets car buyers chop up to $4,000 off the price of a used plug-in hybrid or electric vehicle. It's a speedier way to take advantage of the federal government's tax credit for buying an electrified used car. The credit would otherwise show up on next year's tax refunds.