What major impact does the AMT have on ordinary tax calculations for some taxpayers?

The Alternative Minimum Tax (AMT) is designed to ensure that individuals who benefit from various tax preferences still pay a minimum level of tax. For certain taxpayers, calculating their tax liability using the AMT can result in a higher tax obligation compared to the regular tax calculation. This happens because the AMT operates on a different set of rules that add back certain deductions and exclusions that are normally available under the regular tax system.

As a result, taxpayers who are subject to the AMT may end up with a greater tax liability than they would have if they had only followed the regular tax laws. This increased liability is a significant factor that can affect individuals with higher incomes or those who have many deductions, as it limits the tax benefits they can claim. Thus, the correct answer highlights the transformative effect of the AMT on overall tax obligations.