If you paid to have the labor done and have receipts you can include it in the cost of car. If you had a car you bought for $50K and added $20K in improvements not counting your personal labor your cost basis would be $70K and no income tax would be owed unless you sold it for over $70K and only on the amount over $70K. Just don't play games trying to put the money in an account a little at at time. That's a red flag! Just put the full amount in and they won't think you're doing anything wrong.