Your tax liability is the tax you actually paid, regardless of refund. For example, if you paid $5000 in withholding and received a $1000 refund, your tax was $4000. Or, if you had $3000 in withholding and owed $1000 when you filed, your tax liability was still $4000.
Your EV credit can’t exceed your tax liability, and your other credits count first. Look at your 2020 tax return and determine your tax liability. Then remember that the child tax credit will be $1000 higher per child (or $1600 higher if the child is age 5 or less), so your liability will be lower. That updated tax liability is the largest your EV credit would be if you buy in 2021.
You could increase your tax liability by changing from pre-tax retirement contributions to after-tax (Roth) or by deferring planned charity donations, or by increasing your taxable income in some other way. It’s impossible to give comprehensive suggestions, you may want to see a tax planner if you want to buy an EV this year.
