The Alternative Minimum Tax (AMT) came into being with the Tax Reform Act of 1969. Its purpose was to target a small number of high-income taxpayers who could claim so many deductions they owed little or no income tax.
The tax laws give preferential treatment to certain kinds of income and allow special deductions and credits for certain kinds of expenses. The alternative minimum tax (AMT) attempts to ensure that anyone who benefits from these tax advantages pays at least a minimum amount of tax. The AMT is a separately figured tax that eliminates many deductions and credits, thus increasing tax liability for an individual who would otherwise pay less tax.
The after-tax returns listed in Morningstar reports do not include the Alternative Minimum Tax.