I think even the 2106 is questionable in some cases.  If the employee was just too lazy to submit the reimbursement forms then no deduction.  The IRS rep at the National Tax Forum I went to this summer wanted proof from the employer that the expenses were not eligible to be reimbursed.  I strongly recommend the accountable plan approach though.  I hate leaving money on the table, especially for 2018+.

That said, the employee/owner could put his CEO hat on, and make a policy that says "we don't reimburse for business mileage."  Then put his employee hat on and complain about how he's getting screwed by his employer. 🙂

Rick