When you take the per-mile deduction, and portion allowed for each mile "is" depreciation. As you know, the per-mile deduction changes every year, which means the amount of depreciation per mile also changes every year. When you sell or otherwise dispose of the vehicle, you are required by law to recapture all prior depreciation and pay tax on it. So to report it correctly you need the business miles driven each year (which you should already have) and you need to know how much depreciation was taken for each mile, in each year. To get that, see the chart at https://www.smbiz.com/sbrl003.html#dsm so you can do the math to figure the total depreciation taken for all years you owned the car and claimed any business use.
Your cost basis on the car is what you paid for it, minus all depreciation taken. So with your sales price, I would expect you to "NOT" have a taxable gain unless you drove a few hundred thousand business miles each and every year you claimed business use. But even so, this does not negate your requirement to correctly report the sale of this vehicle.
