Case 1: If you purchased a vehicle for $40,000 and the corporation reimbursed $40,000 for bonus depreciation and now you trade in the vehicle for $45,000 and the dealer gives you $20,000 for the trade-in, you will have $20,000 profit on the trade ($20,000-zero basis). Now you can report the $20,000 gain on your personal Form 1040 using IRS form 4797.
Case 2: If your C corporation reimbursed you using IRS mileage rates. For the miles you were reimbursed, the mileage rate depreciation totaled $12,000. Now during the time of trade your basis is $28,000 ($40,000-$12,000). The dealer gives you a trade-in allowance of $20,000. You have a loss of $8,000 that you deduct from the IRS Form 1040 using IRS Form 4797.