If you have deductible commuting expenses, there are two ways to figure out how much you can write off. One is to take the IRS standard deduction -- 55.5 cents per mile as of 2012 -- for every mile you travel by car. The other is to calculate the actual cost. A lot of commuting doesn't meet the IRS deductible standard, however.
Commuting from your house to your office or job site is not a tax deduction. You can, however, write off commuting between job sites: Your office to a client, your home office to a job site or from one job to another. If you start using a temporary workplace, those commuting trips are deductible. For example, if you spend a week driving to training sessions at some place other than your regular office, those trips are deductible.
If you think there's a way to turn your home-to-work commute into a business expense, think again: The IRS has heard it all. Making business calls on a bus or working on your PowerPoint presentation while on the subway doesn't turn the trip into a deduction if it didn't qualify already. Placing your business logo on your car or packing case files or tools in the back seat to take to work doesn't let you write off the trip.
If you want to deduct the actual expense of driving your car for work, rather than standard mileage, that includes the work-related percentage of your gas, oil, repairs, new tires, parking fees and other expenses. Keep track of your expenses for the year and also how much mileage you drive for work and for personal use. If you spend 40 percent of your time driving for business, you can deduct 40 percent of your total expenses.
When you're self-employed, you report your deductible commuting costs as a business expense on Schedule C. If you're an employee, and your employer doesn't reimburse you for all your commuting costs, you can only deduct work trips if you itemize. Unreimbursed work expenses are among the "2 percent" expenses listed on Schedule A. You add all such expenses together and subtract 2 percent of your adjusted gross income. Whatever remains is your deduction.
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