When you enter vehicle expenses for any purpose (Schedule C, Schedule E, Form 2106) in your tax return, you are asked to enter the number of miles driven for the entire year, the number of miles driven for business purposes, and the number of commuting miles.
These values are used to determine how much (what percentage) your car was used for business purposes.
The assumption is that: total number of miles driven - business miles - commuting miles = personal miles.
If you are seeing a message that one of the numbers is invalid, it is telling you that for the numbers that you entered, there was nothing left over for personal miles. The business miles + commuting miles was greater than the total. So, the program assumes that the error is in the number of commuting miles.
Actually, you should revisit the section where the miles was entered to be sure all of your numbers are accurate. But remember, the total must be greater than business + commuting.
To be sure you understand what is considered commuting miles, take a look at the following information from TurboTax help content:
Commuting miles are the miles you drive to and from your regular place of employment. They are a personal expense and are not deductible. If you are self-employed and your office is located in your home, you can deduct miles you travel to meet with business clients or perform other business-related functions. If your office is located away from your home, you cannot deduct miles you travel to go to your office. If you are an employee, your regular place of employment is an established office of a company where you work as either a permanent or temporary employee. You cannot deduct mileage even if you work in the car while commuting to your regular place of employment. You can deduct: - Travel between two or more workplaces in the same day (even if it's for the same employer) - Travel between your home and a temporary work location inside your metropolitan work area (if you have no regular place of business) - Travel between your home and a temporary work location inside or outside of your metropolitan work area - generally for projects that last only a few days or weeks - if you have one or more regular places of business.
Note: Deducting vehicle expenses as an employee receiving a W-2 using Form 2106 is no longer allowed on the Federal return for 2018 through 2025 due to the Tax Cuts and Jobs Act. The remaining information regarding how TurboTax calculates the mileage based on your inputs is still valid.
[edited 4/7/2020 | 8:45 am PST]
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