It's based on tax liability and vehicle, not on income. For instance, if your tax liability after other credits (not what you owe after withholdings and payments) is $6,000, that's your limit, if the vehicle is qualified...which Tesla is no longer. If you bought a Chevy Bolt in the first quarter, your limit is $1,875 and it no longer qualifies at all after that. I know, because I got $7,500 on a new 2014 Chevy Volt on my 2016 return and I'll get $7,500 on a new 2018 Chevy Volt on my 2019 return, as I purchased it in Q1 2019 when the credit for GM was still the full amount.
