In addition to the 56.5 cents per mile, you are also allowed to claim an expense for parking fees and tolls that are associated with the business use of your car.
The optional standard rate has some restrictions such as the number of vehicles used at one time and the prior use of Section 179 depreciation.
An alternative to the optional standard rate per mile is to compute the business portion of the actual expenses for gasoline, repairs, insurance, depreciation, licenses, etc.
You can learn more about federal income tax issues at www.irs.gov.
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