The question I would ask a tax accountant on this matter is, if you are required to declare a Capital Gain on such a transaction, then could you also declare a Capital Loss should the transaction (or previous / subsequent transactions) result in a sale below the depreciated value.
I'm not convinced that the question could be answered without professional advice based on a taxpayer's individual circumstances. I would think it would revolve around whether the taxpayer is in the business, evan as a private seller, of buying and selling cars. I *am not* a tax professional, so that is pure conjecture.
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For those residing in Canada, just as an FYI, the above would be a factor. And if you were required to declare the sale as a Capital Gain, it would then qualify as eligible for inclusion in your $800,000 lifetime Capital Gains Exemption (max $400,000 per transaction). Note that sale of your Primary Residence (the home you normally reside in) is exempt from Capital Gains under normal circumstances (not engaged in short-term flipping of houses).
If there were to be a taxable Capital Gain (from any type of transaction), then 50% is tax free and the other 50% is taxable.
Most ordinary taxpayers in Canada would have reporting requirements for Capital Gains mostly with stock investments, and losses can be deducted and carried over from year-to-year. Capital Gains within your Registered Retirement Savings Plan (RRSP) are always tax free.