回复:不是说非得NR才可以吗?可我们填的是1040啊
Sorry, didn't read your post carefully. If F-1 file tax with 1040 NR, they don't need to pay SST.
My understanding is that if you have maintained F-1 for over 5 years, you have to file tax as resident alien with 1040 starting 6th year, and you need to pay SST at that time.
Please see the link.
http://www.irs.gov/businesses/small/international/article/0,,id=129427,00.html