Hi, my husband is an American citizen and I am a Japanese national without American citizenship nor LPR status. We are currently residing in Japan.

We are now collecting papers needed for my immigrant visa, but a question regarding sponsorship came up. My husband is the petitioner, but his income past three years was earned in Japan and he hasn't filed the federal tax return during the period.

I would like to know whether an American citizen earned income outside the U.S. can be a sole sponsor of the family-related immigration.
(He will lose his current job when we move back.)

If he can, he needs to file the past three year tax return immediately.
If not, we need a joint sponsor.
This is my understanding. Please answer the above question and let me know my understanding is correct.

Thank you for your help.

First of all, even if he is working outside the US, he still needs to file US tax returns. However, he does not need to pay taxes on the first approx. $85000 of income (exact number is on the 1040 forms). He will still be the primary sponsor and need to provide tax returns.

Secondly he will need to establish domicile in the US.

If he doesnt have the income yet after that, he can get a joint sponsor.

Indeed he needs to file those back taxes as soon as possible - he will still be your main sponsor; but since foreign income does not quite count for sponsorship, you will be better off lining up a sponsor who is a USC and has US income.
Also, since you both live in Japan, you might be eligible to file for Direct consular Filing (DC) which tends to be quicker than the long road with the Service Centers in the US.
Good luck ,L.

Thank you guys!
I have looked at the IRS website and am now working on his tax returns.
We are going to ask his relative to be a joint sponsor.
Hope everything goes well.
Thanks again.