SINGLE MARRIED W2

[bine22]

That question is totally irrelevant, as filing single is not an option

[akj1357]

I want to file 2016 return as "Married Filing seperate" without amending my 2015 return. Is it possible?

[bine22]

the returns for 2016 and 2015 are independent. But since your return for 2015 was wrong, you should amend it (and ideally before filing the 2016 return). If you have to pay back taxes, interest will accumulate, so the sooner the better. Also, wrong tax returns may affect future visa/green card applications. And it is always better to amend before the IRS figures out you filed a wrong return.