Most likely - you entered some information incorrectly
When you enter information from your W2 form - be sure to enter separately amounts from boxes 1, 3, and 5 - there should be different amounts
You also need to determine if you was a resident or non resident for tax purposes.</p><p>if you are a resident - you will use the form 1040 (or simplified forms 1040A, or 1040EZ
if you are a non resident - you should use 1040 NR - http://www.irs.gov/pub/irs-pdf/f1040nr.pdf - most online services do not allow to file electronically this form
To find out your status - see the IRS publication 519, U.S. Tax Guide for Aliens - http://www.irs.gov/pub/irs-pdf/p519.pdf
As you said that the balance is large - please verify how that balance is calculated - is that income tax only? any penalties added? did you calculate additional social security and Medicare tax?
Please provide me with the form you used , lines and amounts - I will try to help you with directions
Let me know if you need any help.
If you are clear that you are a resident for tax purposes - that would simplify your tax return - and you may file online.
If your employer did not withhold FICA taxes (social security and Medicare) - you likely provided them incorrect information - might be not intentionally - and may not simply say that was their fault..
If you are responsible for FICA taxes - that still need to be determined.
Generally as you are in the US since 2002 - you ARE liable for FICA taxes starting on 1 January 2007. However depending on your country of residence - you might be able to claim tax treaty benefits as long as you are on F1 visa.
In this situation - it might be very beneficial to have a tax professional helping you with tax preparation.