The Withholding Summary report lists all sources for Federal, State, and Local Withholding by form (W-2, 1099-MISC etc.). At the bottom of the report, there is a All Other Withholdings field that applies to only federal withholding.

Sources for withholding that are reported in the All Other Withholding field are:

• Form 8959 Line 24, Total Additional Medicare Tax withholding
• If the taxpayer is a dual resident filing Form 1040 U.S. Individual Income Tax Return, then from the Residency Worksheet Line 3, Tax withholding not already included (Form 1040, line 25)
• If the taxpayer is a dual resident filing Form 1040-NR U.S. Nonresident Alien Income Tax Return, then from the Residency Worksheet Line 3, Tax withholding not already included in the return (Form 1040-NR, Line 25)

Note that any link in the information above is updated each year automatically and will take you to the most recent version of the document at the time it is accessed.