Individual taxpayers who don't itemize their deductions are entitled to a standard deduction amount by which to decrease ADJUSTED GROSS INCOME in arriving at taxable income. Amount of the standard deduction varies by the type of taxpayer and changes each year. A schedule of standard deductions is simply found in the instructions for the federal form 1040. Every state may also use a standard deduction format though the amounts and computations differ from federal and from state to state. Certain taxpayers may not be entitled to use the standard deduction. An illustration of this would be a married filing separate taxpayer. If one taxpayer itemizes then other is needed to by law even if the married filing separate taxpayer is unknowing of what is included on spouses separate return. A reason for this may be the prevention of pooling and duplication of deductions.