It's the destination, mileage, and purpose. That can be a word file. It can be the output of a mileage app. It can be scribbled on the back of a napkin. It's not hard to document all of that.

Yes, 13k miles is a lot. But I'm entitled to that deduction and I have the documentation that the IRS requires to substantiate it. There's no way I'd listen to any accountant who warns me not to take it. There's no reason to be scared of the IRS if you are playing by the rules they set.