Can I add my mileage separately if it was already in my original tax form 12a?

[macuser_22]

12a on what form?  W-2?

If a code L then you do not enter it anywhere else.

[Vanessa · Accepted solution]

Mileage as an employee is no longer tax deductible.  You would not enter it anywhere.

 If you are seeing it in box 12a code L, this has been excluded from your taxable income so you are not being taxed on your reimbursement.