What is a key factor that disqualifies a couple from filing jointly while one spouse itemizes?

When a couple considers filing a joint tax return, they must both adhere to the same tax treatment regarding how they deduct expenses. If one spouse itemizes deductions on their tax return, the other spouse cannot take the standard deduction; they must also itemize, regardless of whether it would be more advantageous for them to take the standard deduction.

This principle is established by the IRS, which requires that if either spouse itemizes deductions, both must do so. Therefore, when one spouse itemizes and the other does not, this disqualifies the couple from filing a joint return under the rules that govern filing status.

The correct choice highlights that the standard deduction for the spouse who is itemizing effectively becomes $0 when filing jointly, making it impossible for the couple to take the benefits of combining their incomes and deductions under that status. The other options do not accurately reflect the constraints placed on couples regarding itemizing versus taking the standard deduction in joint filing scenarios.