Expenses reimbursed by your employer aren't deductible on your tax return. Also, commuting expenses cannot be written off. That said, if your employer reimbursed you 40 cents per mile, that's a dime less than the IRS allowance of 50 cents per (see http://www.irs.gov/newsroom/article/0,,id=216048,0... BUT, 10 cents times 10,000 is $100. It's highly unlikey that $100 exceeds 2 percent of your AGI, but maybe you could include it with other unreimbursed business expenses and qualified miscellaneous expenses. Just be sure to have proper documentation.