@anirudhrap , having read through your original post and the response by @MarilynG1 , which I agree with, just wanted to point out something in your post -----
(a) presumably you entered USA with F-1 anytime within five calendar years of 2020 ( per your post that your exempt status was valid till status adjustment).
(b) Since your status adjustment was on 10/1/2020, you would have Non-Resident Alien for the whole of 2020. And therefore you filed a return on form 1040-NR;
(c) Granted that you could have exercised your first year choice to be treated as a resident for tax purposes, -- because you met 1. at least 31 days present in the USA,; 2. you would be meeting the substantial presence in 2021; 3. you were filing your return after having passed the SPT ( Substantial Presence Test); 4. you wrere not a Resident Alien for tax purposes in 2019; 5. have valid SSN for work
(d) You can therefore indeed amend your return ( as noted by @MarilynG1 ) to form 1040 , filing as a resident for tax purposes --- use TurboTax to prepare your amended return , attach a copy of the original 1040-NR, marked for reference only, attach a note requesting that you wish to be treated as a resident for tax purposes for the WHOLE year 2020. I say the whole year because the start of the year begins on the first day you were physically present in the USA . Thus if you had any Non-US sourced income during the whole of 2020, all of this would come under US tax purview ( note that US-India treaty conditions assertions may/ may not apply , based on facts and circumstances in your particular case ).
Does this help ?
