Context is basically as follows. Last year I worked for Google Research as an AI researcher as a GC holder in the US. We wanted to move back to our home country X for an extended period of time, so our young kids would learn their language properly and as part of that I quit my job in the US in August and immediately found a new one in country X. I was planning on maintaining GC status and move back to the US within 12 months.
Now we decided earlier this year that we won't return, so we won't try to maintain GC status. The last day I was in the US last year was in early September and I have a fair amount of foreign income paid from country X to my bank account in country X with country X taxes automatically deducted.
I'm trying to parse the US tax code to figure out what my filing status is? Is it Dual Status with my last day in the US last year as the end date after which I don't need to report any country X income to the IRS? Should I file resident taxes for the whole year and report all my country X income, since I haven't reported to DHS or anyone else that I'm relinquishing my GC? Country X considers me to be a tax resident from the day I arrived last year, since that is when my permanent stay started. My understanding is that I wouldn't even have to report dumping the GC and that filing a non-resident return would basically do that for me?
UPDATE: Seems like the IRS website has language that is easier to parse:
However, you are still considered to be a resident alien of the United States for U.S. income tax purposes, until you: (1) voluntarily turn in your green card to USCIS and renounce your U.S. immigrant status; (2) have your immigrant status administratively revoked by USCIS; or (3) have your immigrant status judicially revoked by a United States federal court.
In other words, I need to file a resident return for the whole year.