I have been searching for the answer and I've seen conflicting answers from different people. When amending a return, Turbotax prints out the 1040X along with a 1040 and all the schedules, and I've seen tax experts say that you should include everything when you mail the IRS (the 1040X, the amended/changed 1040, and all the schedules) but I've seen other sources say that you only send the 1040X itself plus any schedules that change. Obviously the amended 1040 itself changes, but in my case none of the schedules are different, I had just missed a 1099R which added a small amount of interest that was taxable (net additional tax was a few hundred dollars). Do you send just the 1040X? The 1040X plus the modified 1040 but not schedules? The 1040X and the whole amended return?
Also, how detailed should the 1040X explanation be? Can it just be "I missed a 1099R" or do you have to include line by line explanations?