In order to deduct business driving, you need to meet substantiation requirements. Typically this is done by entering required information in a written log or mobile app. One attorney with 5 law offices across the state couldn’t deduct mileage because his attempt at reconstructing a mileage log was inadequate. The Tax Court said a reconstructed mileage log based on appointment entries on an iPad calendar and credit card statements not entered into evidence fell short; they don’t corroborate the business purpose of each trip.