If, like most people, you have have lots of expenses in the course of a year, you may be able to write some of them off on your taxes. To claim most deductible expenses, you have to itemize your taxes, but you can claim some items even if you take the standard deduction.
If you run a business, either full time or on top of your day job, you can deduct your business expenses: office supplies, travel costs when meeting with clients, membership in professional groups and the cost of a home office. The IRS requires you to separate business and pleasure: If you use your personal car for business, you only claim your business use as an expense. You claim business expenses on Schedule C, your business-income form, and you can write these expenses off even if you take the standard deduction.
Adjusted Gross Income
You determine your adjusted gross income (AGI) on the front of your 1040 by adding or subtracting various items to your taxable income. This is where you get to claim expenses even if you don't itemize. If you're a teacher, for example, you can deduct up to $250, as of 2012, for books and supplementary materials you buy for the classroom. You can also write off interest on your student loans, part of your self-employment tax and the expense of moving more than 50 miles for your job.
You can deduct many of your and your family's medical expenses, including doctor bills, dental bills, eyeglasses, prescription meds. The IRS specifically excludes certain other expenses, such as cosmetic surgery, non-prescription drugs and vitamins. You have to itemize to claim this deduction, and you can only claim expenses greater than 7.5 percent of your AGI. If 7.5 percent of your AGI is $7,500 and you have $9,000 in deductible medical bills, all you can claim is $1,500.
If you itemize deductions, you can write off mortgage interest and mortgage-insurance premiums you pay during the year as a deductible expense, provided it's on your personal home or vacation home. This applies not only to houses but to condos and mobile homes. If you prepay interest as part of the closing costs, you may be able to deduct that money the year you closed, but you can also prorate it over the life of the loan.