FYI, what you're having withheld does not affect whether you get the full tax credit. The amount you're having withheld each paycheck is just based on what you think your tax liability will be at the end of the year. This is why there are refunds. If you overestimate, you get a refund; if you underestimate, you owe more taxes.

Your tax liability is determined at the end of the year when you file your taxes. If your tax liability is > $7,500 before the EV tax credit, you will get the full value of the tax credit deducted from your taxes.

If your tax liability is < $7,500, you will have zero tax liability, but you will not get refunded the difference. For example, if your tax liability was $5,000, you would not get a refund for $2,500, your tax liability would go to zero and you would owe nothing.