I changed status from non-resident to resident last year (2018) because I went from an OPT VISA to H1B visa. I haven't paid the FICA (Medicare and social security) for the whole 2018 year because my employer treated me as non-resident for the whole year. I then tried to use Sprintax but it said I am a resident so I used TurboTax and got a refund already (with a w2 showing 0 on FICA taxes paid).
Now my employer said I have to pay him back of the FICA taxes I did not pay from October to the end of the year. Should I request another w2 for 2018 showing I paid the FICA from October to the end of the year?
Did Turbotax calculate that I owe the FICA taxes and lowered my refund? How do I know?
