Yes. If the amount you receive on the sale is more than you paid for the car, the different is taxable gain. However, as is the usual case with a personal vehicle, where the value typically declines over time, any loss on the sale of a personal vehicle is not deductible (you cannot take a capital loss on personal use property).
Advance payment of current tax liability based either on wage withholdings or installment payments of your estimated tax liability. To avoid penalties, you generally must pay to the IRS either 90% of your final tax liability, or either 100% or 110% of the prior year’s tax liability, depending on your adjusted gross income.