Unless you keep records of this, you likely won’t be able to deduct your driving expenses. That’s what one lawyer who worked for the state as well as having his own law firm learned from the Tax Court. He kept a list of dates, locations, mileage, and parking costs, along with bank statements, various receipts, and a copy of a calendar. The calendar contained writings of names, times, and locations but did not distinguish which appointments and locations were for personal reasons, for his job, or for his law firm. Result: No deduction for business driving related to his law firm was allowed.