I'm doing a friend of mine's taxes. He's a union worker and frequently is at different job sites. For 2013, he did not keep track of his mileage (or other years for that matter). I realize that no two situations are the same, however my question is... is there a way/method to estimate his mileage that is reasonable/acceptable to the IRS? I don't want to just throw a number on there that he comes up with and get him in trouble. In addition, the person who did his taxes before missed this deduction, so I'm going to look into amending his prior returns, which is another reason why I wanted to see if there is an acceptable method to estimate business mileage. Any responses are appreciated, thanks.

You have until April 15 for taxes. Starting now, have him calculate the mileage driven for 6 weeks and then, if he considers it average, use the 6 weeks to proportion the year. Amending his prior returns may be a little bit more problematic. Have him start recording 2014 mileage now. The safest way would be to use actual expense cost, if he kept those records.

I was always under the impression that to deduct business milage on your taxes... you needed (actually REQUIRED) to keep a log of business use VS personal use to back it up.

Smoothy is right about keeping the log.

However, Ma0641's methodology is acceptable to the IRS as long as it is reasonable and consistently applied.

Thanks for your responses!

Glad to help!