@Anja_SG , from the instructions etc. for the form I 407, it is a notification that you have abandoned the LPR status. The processing part by USCIS is to record / update their files. Thus I think if you sent the I-407 on 12/31/2019, then there is sufficient expectation that you have abandoned LPR on that date .\
Hence my question whcih year are you trying to file and questioning about. You migrated to Singapore in 2018, and filed I-407 in Dec 2019--- therefore I assume that you have filed your US returns on world income for 2018 and 2019. For 2020 you are a Non-Resident Alien for US tax purposes and therefore taxed ONLY on US sourced/connected income. So why are you filing 2020 ? Do you have or will have US income in 2020 ?
