To enter a Foreign Tax Credit (FTC) carryback on an amended Form 1116:

Part I, Line 12:
This is where you enter foreign taxes paid or accrued. If you are carrying back a foreign tax credit, you'll enter the carryback amount here, adjusted for the relevant tax year.

Part III, Line 10:
On this line, you enter the total amount of foreign taxes paid or accrued. Ensure that the carryback amount is reflected correctly as part of this total.

Amended Return Specifics:
Check the "Amended" box at the top of Form 1116 if available, or indicate that it's an amended Form 1116.
Attach the amended Form 1116 to Form 1040-X, Amended U.S. Individual Income Tax Return.

Explain the Changes:
On Form 1040-X, Part III, provide a detailed explanation of the changes being made to your original return, including the FTC carryback.

Supporting Documentation:
Include any necessary documentation that supports the FTC carryback, such as statements or schedules showing the calculation of the carryback amount.

Additional Tips:
Complete the Amended Form 1116:
Use Form 1116 to calculate the FTC for the tax year you are amending.
On an amended return, you will use the tax year for which you are claiming the carryback, not the year the foreign taxes were paid or accrued.
IRS Instructions: Follow the IRS instructions for Form 1116 and Form 1040-X carefully, as carrybacks can be complex and may require additional calculations or adjustments.