Deductions & credits

Dave, I am in the same boat as these other people. However, I was upside down on my trade. I owed $26,000 and the dealer gave me $20,000. So what is the sale price? The price of the new vehicle is that the unpaid cash balance due on delivery (found on the bill of sale from the dealership) minus title fees, etc. There is also listed credit insurance as a non includable cost of the vehicle, what is that? The new vehicle is a truck and I am going to use the section 179. 

Also, what is the amount that I put in Turbo tax for the traded in vehicle in the section Sales Price (for the old vehicle's expenses in the vehicle summary section) . It askes what is the business portion of the sales price. Again do I use the $20,000 and multiply by my usage to get the number or do I use the $26,000 loan amount. I just want to stay consistent with my numbers between the old vehicles and the purchase of the new vehicle.

Thanks for any guidance!