@yashK , disagreeing with @LinaJ2020 --- based on our earlier discussion , you were a Non-Resident Alien for 2019 but under H-1B ( as an employee and not a trainee ) you are not immune to FICA taxes . So yes your employer will withhold Federal, State and FICA taxes from the date of adjustment. Also note ( and perhaps I should have pointed out earlier ) that a NRA you file form 1040-NR ( not supported by TurboTax ).
You always have the option of filing a form 1040 under the first year choice -- 1. you have been present for 31 days continuously; 2. have been present at least 75% of the days in the test period of Oct.1 through 12/31/2019; 3. you have not been a resident / resident for tax purposes during the previous year; 4. you will be a resident for tax purposes by the time you file in April of 2020. This may be advantageous for you ( especially if you have had zero foreign income during 2019 ). All you need to do is add a note along with your return stating the above items in a letter and requesting that you wish to be treated as resident for tax purpose for 2019. This of course means you file by mail because that will get human intervention.
Namaste ji
