To itemize deductions means to list and claim specific eligible expenses on your federal income tax return that can reduce your taxable income. Instead of taking a fixed standard deduction amount, taxpayers who itemize add up allowable expenses such as mortgage interest, state and local taxes, charitable donations, and unreimbursed medical expenses, among others, and subtract the total from their adjusted gross income (AGI). This process is done on Schedule A of Form 1040. Taxpayers choose to itemize deductions if the total amount of these expenses exceeds the standard deduction available for their filing status, which can help reduce their tax bill more effectively. Itemizing requires keeping documentation like receipts or statements to substantiate the deductions in case of an audit. In summary, itemizing deductions means carefully listing and claiming individual deductible expenses to lower taxable income, as an alternative to taking the standard deduction.