I did an undergraduate degree between 2008 and 2013 under an F1 visa. Then, right after, I started a graduate degree (PhD). I had to apply for a new F1 visa after I graduated in 2013, but I kept my social security number from 2010.
My question is: does the 5 year non-resident alien status for tax purposes reset with a new F1 visa or is that period once in a lifetime? In other words, should I have had to file 1040 instead of 1040NR?