Mileage reimbursement

[HumFly]

If I’m being reimbursed .42 a mile & IRS rate is .62.5 a mile, how do I claim the remainder 

[LarryL20]

You did not state if you are employee or an independent contractor.  This response is based upon you as an employee of your company.

Employee business expenses can no longer be deducted on your tax return.  The exceptions are for an Armed Forces reservist, qualified performing artist, fee-basis state or local government official, or employee with impairment-related work expenses. 

Therefore, unless you would satisfy one of the exceptions, the difference between the 42 cents per mile reimbursement and the IRS allowed rate of 62.5 cents would not be allowed as a tax deduction.  Additional information is in the instructions for Form 2106 (Employee Business Expenses).