Thanks HACKITOFF.
In 2017, I am not US resident. The foreign income tax credit is from the general income tax, over $1000 credit unused. The problem is I tried to enter carry over foreign tax credit in turbo tax, but because i have no foreign income in 2019, it seems i can only get 0 foreign tax credit, that is why I am asking if the only option is carry back and how can I do? Carry back to 2018? But the limit are used up in 2018. Please help to advise. Many thanks!
