@manukris , please note that once your visa was adjusted , you are no longer on OPT -- you are an employee .
Thus for 2023 till the date of adjustment you were on OPT, there after you are on work visa and therefore NOT immune from FICA requirements.
You know that O-1 is a Non-immigrant work visa ( just like H-1 and many others ).
Does this make sense ?
how can I help you more ?
