When to mail my FICA refund claim

Hello everyone,

 

Last year I was a J1 scholar at a university and considered a non-resident. However, my employer withheld the Medicare and Social Security taxes. I contacted them and they said it was not possible for them to give me a refund. So, I talked to Sprintax and they prepared the forms 843 and 8316 for me.

 

I have already e-filed my federal tax return and paid the amount owed.

 

My question is: can I mail my FICA return claim already? I already have all the documents (W2, DS-2019, I94, etc) needed.

 

Thanks in advance!