Hi! My son bought a car w a grandparent loan. However, he forgot to write off taxes in his filing. He's my dependent. Can I write off the purchase? Car is in my name.

Purchasing a car is not tax deductible. However, if they purchased an EV or Hybrid, there "might" be a tax credit.

Q.  Can I write off the sales tax paid on the purchase? 

A. No. In order to take the deduction, you must have actually made the payment.

The sales tax deduction is only an itemized deduction.  To get any benefit, your total itemized deductions must except your standard deduction ($12,950 Single and 25,900 Married filing jointly).

For a dependent, his standard deduction is the greater of $1150 or his earned income + $400 (but not more than $12,950). 

Thank you both for your very helpful response!