the calculations are complicated, so you need to review the 1116 and the 1116 comp worksheet.
a quick summary of the FTC computation. the foreign dividends are reduced by an allocation of your itemized or standard deduction based on the ratio of it to your gross income. this reduction is on line 6 of the form. (see 1116 instructions for what's included on in gross income). this is your net foreign income. this net is divided by line 15 of your 1040 to come up with another %. this % is applied to line 16 of 1040 + schedule 2 line 2 to come up with the current year allowable FTC.
another way to put it is if your effective federal tax rate before the FTC is less that the effective rate of foreign taxes (foreign taxes divided by net foreign income). you won't be allowed all the foreign taxes you paid. you may be able to carryback the unused to 2021 any unuse may be carried forward 10 years.
