A tax deduction is an expense that you can subtract from your total taxable income, which reduces the amount of income that is subject to taxation. Common examples of tax deductions include mortgage interest, charitable contributions, and medical expenses. By lowering your taxable income, tax deductions can help you pay less in taxes. Tax deductions are often available to individuals and businesses, and they can vary based on specific criteria set by the Internal Revenue Service (IRS). It's important to keep accurate records of your expenses to claim these deductions when filing your tax return.