Read the rules here : https://www.irs.gov/forms-pubs/about-schedule-c-form-1040
Thank you, but this is where I started. It is not obvious. I was told by several people that words "depart" and "leave" clearly mean "permanently leave" there, but that is not clearly stated anywhere.
If you were not leaving permanently then you would have no reason to file the 1040-C ... you would continue to file the 1040 or 1040NR as needed.
But link you sent me says:
If you furnish the IRS with information showing, to the satisfaction of the IRS, that you intend to return to the United States and that your departure does not jeopardize the collection of income tax, you can get a sailing or departure permit by filing Form 1040-C without having to pay the tax shown on it.
So, if I intend to return, I have to file it too, just no need to pay. Or I don't have to file at all?