The IRS has a publication for this: https://www.irs.gov/publications/p544
One, put a number in the blank. That way it shows you did dispose of the vehicle and it won't keep showing up.
Two, we almost always sell vehicles for less than we bought them. Therefore they are sold at a loss. Therefore we don't need to recover depreciation, since it did actually...depreciate!
Three, you bought the vehicle personally, it depreciated, and you sold (donated) it personally. You did not get anything for the sale. Your sale price is therefore 0.
Four, you owned the vehicle personally, not in the business. Therefore the value of the donation (remainder value after depreciation of your asset, almost always lower than your purchase price) is a personal deduction, not a business deduction. "In general, charitable contributions are not allowed as a business expense on the Schedule C. However, if you made a payment to a charitable organization that was not for charity nor a gift, you may deduct the payment as an expense to the business. [copied from another TT discussion]"
If you did make a profit on the sale of a vehicle, the detailed calculations would be complicated--the standard mileage rate includes depreciation, so you did claim depreciation if you took the standard mileage rate, but you don't have calculated how much.
"SECTION 4. BASIS REDUCTION AMOUNT For automobiles a taxpayer uses for business purposes, the portion of the business standard mileage rate treated as depreciation is 25 cents per mile for 2018, 26 cents per mile for 2019, 27 cents per mile for 2020, 26 cents per mile for 2021, and 26 cents per mile for 2022. See section 4.04 of Rev. Proc. 2019-46. " https://www.irs.gov/tax-professionals/standard-mileage-rates references this.
