AGI is the acronym for Adjusted Gross Income. It is generally the sum of a taxpayer's income less adjustments (before deductions and exemptions). Many tax benefits and allowances, such as credits, deductions, exemptions, etc., are limited by a taxpayer's AGI.

Generally, limits are based upon a percentage of AGI. Some deductions are reduced by a percentage of AGI until the deduction reaches zero. The two prime examples of this type of percentage limitation are medical itemized deductions (limited by 7.5% of AGI) and miscellaneous itemized deductions (limited by 2% of AGI). Others such as charitable contributions limit the deduction to a percentage of the AGI. Charitable contributions have three AGI limitations depending upon the type of contribution: 50%, 30% and 20%.

Many limitations phase in as the AGI increases between two specific AGI values, thereby "phasing out" (reducing) tax benefit to higher income taxpayers. These phase out levels are inflation adjusted and change every year. To further complicate matters, there are different phase out levels for different filing statuses. Examples of items subject to phase out provisions are:

Personal Exemptions (does not apply in 2010 through 2012)
Itemized Deductions (does not apply in 2010 through 2012)
Education Credits
Education Interest Deduction
Active Rental Losses
Educational IRA Contributions
Conventional IRA Deduction
Taxability of Social Security
Earned Income Credit

Careful tax planning can sometimes avoid or minimize the loss of tax benefits due to AGI limits. If you have advance warning of a large increase in income, it may be appropriate to schedule an appointment to consider alternative approaches to your tax situation.