While Form 1040 is the "face" of your tax return, these schedules are the engines that calculate your final tax liability. The Lettered Schedules (Specific Income & Credits)
You must file if any of the following are true:
If you meet these specific criteria, Schedule R is the only way to claim credit of up to $7,500 (depending on your situation). You cannot claim this credit on the main 1040 or any other schedule.
Required if you owe Alternative Minimum Tax (AMT), self-employment tax, or household employment taxes.