In my previous question, I explained that the IRS still has yet to process my 2019 return, my first filing, which means I won't receive any 2021 stimulus (EIP 3) if its calculation is based upon my 2019 income.
I have significant income from foreign bank account interest. I have an idea of how much it should be, and my 2020 income should put me within the threshold of EIP 3, but I'm unable to accurately determine the amount of that income (I can't log into their online banking portal and I don't think it's a good idea to travel back to visit a branch to reset my password/get my bank statements).
Is it legal for me to file my 1040 timely with a significant overestimation of my income, overpay tax, and file 1040-X for a refund of the overpayment once I can accurately determine the actual amount of my income? Would this manoeuvre still be legal if I received EIP 3 before filing 1040-X?
Upon further examination, my comment on my previous question that my 2020 income would phase out of EIP 3 is incorrect, and my income will stay within the threshold with buffer to spare.