I'm with Meller. You already paid taxes on the original car, the parts that went into it plus the license and registration fees. You may also have a property tax in your state that needs to be paid yearly. Then there is the fact that you probably will not get back the amount that it cost to build. I have never paid taxes on a 'cash' sale of a car - though the buyer will so take care when you make up a Bill of Sale and not 'fudge' the final figure too much for the buyer - that could come back and bite both of you. Yeah, I know, never ever would you do that