Adjusted Gross Income On W2 has the meaning of being a standard measure of income that is used to determine the taxes. AGI is more accurate than gross income as it identifies your income, after deducting certain allowable deductions in the law. It can also be used as a reference point when it comes to defining tax brackets, eligibility to deductions and credits such as the Child Tax Credit or education credits. AGI assists the IRS in the fair application of tax rules through the use of similar income to all taxpayers.