Based on the tax treaty between US and China, I can claim the 3 years tax benefits. I arrived in US on May 10, 2006. So I think my tax treaty expired on May 10, 2009. Yesterday I checked the W-9 I filled last year and found it said my tax treaty expired on Jul 2nd, 2009. I am wondering whether there is a problem of the date.

On H1-B tax treaty deduction is not available. You must pay SS tax, Medicare Tax, federal income tax and state income tax. Your U.S. Tax Return: The U.S. Visas