If one spouse is mentally incompetent (dementia), is the IRS going to care if an amended return with a balance due is only signed by the other spouse?
Publication 17 says,
Injury or disease prevents signing. If your spouse can’t sign because of disease or injury and tells you to sign for him or her, you can sign your spouse's name in the proper space on the return followed by the words “By (your name), Husband (or Wife).” Be sure to sign in the space provided for your signature. Attach dated statement, signed by you, to the return. The statement should include the form number of the return you are filing, the tax year and the reason your spouse can’t sign, and it should state that your spouse has agreed to your signing for him or her.
Signing as guardian of spouse. If you are the guardian of your spouse who is mentally incompetent, you can sign the return for your spouse as guardian.
The spouse with dementia can't really agree with the signing, so the attached statement doesn't seem appropriate. And I'm pretty sure a court has not appointed a guardian. I plan to have the other spouse sign on both lines of the 1040X, with the "by [name], Husband (or Wife)" notation for the first spouse. I can't imagine the IRS is going to reject the balance due payment, which is less than $1,000. The amendment is due to mistakenly over-stating the state tax deduction on federal Schedule A, which the state has already corrected, so the amendment is just to pay now instead of waiting for IRS to eventually catch up.
Publication 17 says,
Injury or disease prevents signing. If your spouse can’t sign because of disease or injury and tells you to sign for him or her, you can sign your spouse's name in the proper space on the return followed by the words “By (your name), Husband (or Wife).” Be sure to sign in the space provided for your signature. Attach dated statement, signed by you, to the return. The statement should include the form number of the return you are filing, the tax year and the reason your spouse can’t sign, and it should state that your spouse has agreed to your signing for him or her.
Signing as guardian of spouse. If you are the guardian of your spouse who is mentally incompetent, you can sign the return for your spouse as guardian.
The spouse with dementia can't really agree with the signing, so the attached statement doesn't seem appropriate. And I'm pretty sure a court has not appointed a guardian. I plan to have the other spouse sign on both lines of the 1040X, with the "by [name], Husband (or Wife)" notation for the first spouse. I can't imagine the IRS is going to reject the balance due payment, which is less than $1,000. The amendment is due to mistakenly over-stating the state tax deduction on federal Schedule A, which the state has already corrected, so the amendment is just to pay now instead of waiting for IRS to eventually catch up.