I did this in Turbotax
car cost $60K, 30% business use (tax basis for depreciation $18K), fully depreciated amount $18K
trade in $30K which was entered as sales price. what I got was the wrong answer I believe. $18K was treated as depreciation recapture but the difference between the trade-in value and the depreciation recapture $12K was treated as long term capital gain. it's as if the basis for the personal portion was zero.
under a multiple asset theory (there is the business asset - % used for business and the personal asset the remaining % then the trade -in value would be split based on business vs personal portion. in this case $9K would be treated as the sales price of the business portion resulting in $9K of depreciation recapture. the remaining $21K of trade-in value would be allocated to the tax basis in the personal portion or $42K. since this would be a loss, it's not deductible. -
under the single asset concept there would be no gain or loss or even depreciation recapture
for example, say I bought a home for $60K took $18K in home office depreciation or depreciation on the portion that was rental before selling it for $20K
this would appear on schedule D as sales price $20K tax basis $42K adjustment to loss $20. no taxable gain/loss - no depreciation recapture. there is no proration of the selling price between the portion that was personal, and the portion used for business/rental
I think the single asset concept is what the IRS prefers but can find no authoritative literature either way.
