Found this at https://www.irs.gov/pub/irs-pdf/i1116.pdfLines 3a and 3b
Some deductions don't definitely relate to either your foreign source income or your U.S. source income. Enter on lines 3a and 3b any deductions (other than interest expense) that:
• Aren't shown on line 2, and
• Aren't definitely related to your U.S. source income.
Line 3a. Enter the following itemized deductions (from
Schedule A (Form 1040)) on line 3a.
• Medical expenses (line 4).
• General sales taxes (line 5a).
• Real estate taxes for your home (line 5b).
If you don't itemize deductions, enter your standard deduction on line 3a.
Line 3b. Enter on line 3b any other deductions that don't definitely relate to any specific type of income (for example, the deduction for alimony paid from Schedule 1 (Form 1040),
line 19a).
