Per IRS Instructions for Form 6251:
Exemption amount. The exemption amount on Form 6251, line 5, has increased to $73,600 ($114,600 if married filing jointly or qualifying widow(er); $57,300 if married filing separately).
Also, the amount used to determine the phaseout of your exemption has increased to $523,600 ($1,047,200 if married filing jointly or qualifying widow(er)).
AMT tax brackets. For 2021, the 26% tax rate applies to the first $199,900 ($99,950 if married filing separately) of taxable excess (the amount on line 6). This change is reflected in lines 7, 18, and 39.
Use Form 6251 to figure the amount, if any, of your alternative minimum tax (AMT). The AMT is a separate tax that is imposed in addition to your regular tax. It applies to taxpayers who have certain types of income that receive favorable treatment, or who qualify for certain deductions, under the tax law. These tax benefits can significantly reduce the regular tax of some taxpayers with higher economic incomes. The AMT sets a limit on the amount these benefits can be used to reduce total tax.
Also use Form 6251 to figure your tentative minimum tax (Form 6251, line 9). You may need to know that amount to figure the tax liability limit on the credits listed under Who Must File, earlier.
To access Form 6251 in the TaxAct program (the TaxAct program transfers the information to Schedule 2 (Form 1040) Additional Taxes Line 1, and adds it to your regular tax):
Note that any link in the information above is updated each year automatically and will take you to the most recent version of the webpage or document at the time it is accessed.