I entered on f-1 visa in aug 2006,
Started opt in dec 2007 - valid till dec 08
Have an approved h-1 starting/valid from october 1st 2008

Started working from august 08, h-1 might start october
What will be my tax residency status?

2 months work on opt then on h-1 b
Am i subject to ss taxes and medicaid taxes

Am i eligible to recive the 5750 india tax treaty exemption i received as a student.

Any links to a free tax calculator are highly appreciated.

Also is per-diem taxable?

Thanks a ton in advance for the expert answers

You will file as a non-resident alien for 2008.

You become liable for Social Security and Medicare taxes thed day your H-1B visa becomes effective.

You SHOULD be able to claim the standard deduction under the U.S.-India Tax Treaty.

The website below has a tax calculator:

2008 Online Non Resident Tax Software - File Form 1040NR-EZ, Form 8843, Form 843, Form W-7, Form 1040NR, International Student Taxes, Non Resident Taxation F1,J1,H1B Visa Taxes, Where to File, Instructions, Mailing Address, Income Tax Forms (http://www.visataxes.com/form1040nrez_home.php)

Perdiem CAN be taxable. It depends on how the per diem is paid and accounted for on the employer's books.