There is no depreciation recapture for a former business use vehicle for which you have always taken the standard mileage allowance until you dispose of the vehicle. Try entering $0 to see if it makes TurboTax happy.
A portion of the standard mileage allowance is considered to be depreciation.
If TurboTax
requires a non-zero answer, check this IRS
explanation of how to calculate depreciation under Disposition.
