You can amend to reflect that if it will benefit you.  If you are an employee (W-2) these expenses go on Schedule A Itemized Deductions where they are subject to the 2% of adjusted-gross-income limit.  This means only the amount over 2% of your adjusted gross income will be deductible on the Schedule A. If you have enough expenses, and typically itemize your deductions, it may benefit you.

Keep in mind that commuting mileage to your W-2 job is not deductible.  You can deduct travel expenses for temporary out-of-town work locations, mileage for when you leave your main work location for a business purpose, and mileage between jobs.

Where do I enter job-related expenses?

https://ttlc.intuit.com/replies/4800418

Amending is done on Form 1040X.  Also, if your return is accepted, you should not try to amend your return until it has been fully processed and you have received your refund or your payment has cleared.

Amended returns have to be printed and filed by mail.  It can take the IRS up to 12 weeks or longer to process them.   If you are due a larger refund than on your original return, your amended return should only show the difference and you will receive a separate check for it.  If you owe money on your amended return, it will show only the new amount owed, you will have to mail a check with the return.

How to Amend?

https://ttlc.intuit.com/replies/3288565

Do you have to mail in mileage log with the 1040X?

No, a mileage log wold be needed if audited. Please keep it with your tax file. 

I have one more question.  I have a mileage log with starting miles on Jan 1 and then i track all miles for busines, commuting, and other miles every month until I get to the miles on 12/31 at year end. My question is do I need to also write down all the places driven specifically every day of the year driven for the business miles, commuting miles and other miles? Ughh, if so I have a lot of back tracking to do. I only tracked the miles every month from begining to end of year. Uggh.

First before you start amending your 2018 return, be advised that IRS no longer allows employee expenses, including vehicle mileage, to be claimed as a deduction. If you are an employee rather than a Self-Employed Business person, you will not be able to claim these expenses on  your 2048 return.  However, some states still allow you to claim an employee business expense and you may wish to check with your state to see if this deduction is allowed on your state return.

With this said if you are Self-Employed filing a Schedule C or filing in a state where this is allowed, then this expense is allowed. Here are the IRS and state requirements for filling out a mileage log., 

According to the IRS, your mileage log must include a record of:

• Your mileage
• The dates of your business trips
• Places you drove for business
• The business purposes for your trips

The IRS also wants to know the total number of miles you drove during the year for business, commuting, and personal driving other than commuting. Although you do not need these specifically to report on your tax return, you will need it in the event you are audited and need tangible proof of your mileage expenses.

edited 04/06/2020 11;10 AM