Commuting expenses between your home and main workplace are never deductible, even if your workplace is far away or you conduct business or haul work supplies or tools during your commute.
If you drive from your usual work site to another job-related destination -- a meeting, to get supplies, or to the airport -- those miles may be deducted.
If you have been temporarily reassigned to another work location that is farther from home, you can deduct the extra distance.
If your employer reimburses you for mileage, however, you cannot deduct these expenses on your taxes.
If you travel to and from a temporary work location (where your assignment is expected to last no more than 1 year) outside your metropolitan area, you can claim commuting expenses.
You're also allowed to deduct commuting expenses between multiple job sites during the same day. For example, if you go directly from your day job to your evening job, you can deduct the commute between those 2 job sites. But if you first go home and then leave to go to your second job, that can't be deducted.