i sell a lot of cars and tax time is def a good time to sell a car, you don't typically see cars selling for more then there worth, but you do end up seeing the nicer versions of cars coming up for sale or lower mileage versions and fetching a bit more money. its like your car, will it sell all year long sure, but your gonna get a lot more low ball offers before the right guy/gal comes at you with the offer your really willing to except. where as tax time your gonna have that more serious buyer, who isnt looking to haggle as much because you knows what you have and knows what he wants. you also see in general an influx in car sales around tax time because all the holidays are over and this is when everyone gets that little extra chunk of cash so they take what they have saved up and spend more money then people do normally buying cars throughout the year.