As a general rule, the Internal Revenue Service expects taxpayers to calculate their own deductions. However, if any deductions claimed seem suspicious to the IRS, the IRS may make adjustments to a return and refigure the taxpayer's deductions.
Most taxpayers are better off taking the standard deduction when filing their tax returns, but others may benefit from itemizing deductions. The standard deduction is simple to figure and is addressed in IRS Topic 551. Some taxpayers are ineligible to take the standard deduction, including married taxpayers filing separate returns or nonresident aliens. Partnerships, common trust funds, and estates or trusts cannot claim the standard deduction.