Alternative Minimum Tax

Two significant changes were made to the AMT for the years 2018 through 2025. All of the changes will be subject to inflation adjustment in years after 2018.

a. The exemption amounts that were scheduled to be $86,200 for joint filers (one-half of that amount for separate filers) and $55,400 for unmarried taxpayers, for 2018, have been increased to $109,400 for joint filers ($54,700 for separate filers) and $70,300 for all others.

b. The AMTI threshold, above which the exemption is phased out $1 for every $4 of excess, has been increased to $1,000,000 for married taxpayers filing jointly and $500,000 for all others. These amounts were scheduled to be $164,100 for joint filers, $82,050 for separate filers and $123,100 for all other taxpayers.

The AMT Exemption amounts for 2014 is $53,900 for single and head of household taxpayers and $83,800 for joint filers and qualifying widow(er) taxpayers

ATRA for 2012 allows nonrefundable personal credits to reduce the AMT.

For 2012 tax years, the alternative minimum tax exemption for a child subject to the Kiddie Tax is limited to the sum of (1) the child's earned income for the taxable year, plus (2) $6,950.

The AMT Patch was the mechanism used by Congress to offset the failure of the tax law to automatically require an adjustment of the AMT brackets for inflation.
This failure, with the resulting need for the annual Patch, has been going on since 2000.
Congress permanently addressed the AMT issue by indexing the annual exemption limits for inflation retroactive for 2012.

AMT stands for Alternative Minimum Tax. The Alternative Minimum Tax was developed in 1969 to make sure that wealthy taxpayers didn't escape paying income taxes. The tax was meant to target high-income taxpayers who may have many deductions and can sometimes avoid paying any income taxes at all.
To make sure that all taxpayers with substantial income are not able to avoid paying tax, the law limits the benefit a taxpayer can receive from favorable treatment of certain deductions and preferences.
The Alternative Minimum tax is computed on IRS Form 6251.
If the Alternative Minimum tax calculation results in a higher tax then the Regular income tax, then the difference is added to the Regular tax computation.

The calculation of alternative minimum tax begins after the Adjusted Gross Income (AGI) is computed. The AMT is basically an add on to the normal income tax computation that is done. After you are done with the calculation of AGI, some of the preferential deductions (standardized or itemized) are added back into the AGI. Next a standard, flat alternative minimum tax deduction is deducted from the total. The remaining figure is known as AMT Taxable Income (AMTI). This AMTI is further taxed at different rates, instead of the current taxation rate. The output is the Tentative Minimum Tax (TMT), and in case if it exceeds the regular income tax the TMT is paid.

$51,900 for single and head of household taxpayers ($50,600 in 2012)
$80,800 for joint filers and qualifying widow(er) taxpayers ($78,750 in 2012)
$40,400 for married filing separately taxpayers ($39,375 in 2012)
There is an exemption phase-out for taxpayers with Alternative Minimum Taxable Income more than $115,400 for Single or Head of Household
$153,900 for MFJ or Widower
$76,950 for MFS.

For Single or Head of Household the phase-out is $115,400 and is zeroed out at $323,000.
For Married filing jointly or Qualifying widow(er) the phase-out is $153,900 and is zeroed out at $477,100.
For Married filing separately the phase-out is $76,950 and is zeroed out at $238,550.