When is it impossible for taxpayers to file an amended return for the American opportunity credit?

The correct assertion is that taxpayers cannot file an amended return for the American Opportunity Credit if the required identification number was not available by the return due date. The American Opportunity Credit has specific eligibility requirements, including the necessity to provide a valid Taxpayer Identification Number (TIN) for both the taxpayer and the dependent for whom the credit is claimed. If this number is not available when the return is initially filed, the taxpayer cannot retroactively claim the credit through an amended return. The identification number is essential for verifying eligibility and ensuring proper processing of the credit.

Other scenarios, such as how the original return was filed, whether the tax liability is zero, or the timing related to the fiscal year, do not inherently restrict the ability to file an amended return under the stipulations of the American Opportunity Credit in the same manner.