Hi, I am in US working on H1 and my wife and Kid on H4. I am filing my tax under Married filing Jointly. Since it has been just few months in US even If I don't claim for Exemptions for my Wife (Section 6 in Form 1040) I get the same refund. Now my Question is do I still need to file for her ITIN?

When did you enter the U.S. on H1-B? You may have to wait till you complete SPT in 2010 to file your tax return. On the joint return you must attach W-7 (ITIN application). Your U.S. Tax Return: The U.S. Visas

Thanks for rth equick reply. I came in Sept 2009. What
Is SPT?

You have two choices
Choice 1: File non-resident tax return. Claim moving expenses.

Choice 2: You can file resident tax return as Married Filing Jointly. You will have to wait for 5 months to file your tax return till you meet the Substantial Presence Test in 2010.Your U.S. Tax Return: Substantial Presence Test

You will get standard deduction of $11,400 and exemptions ($3,650 each) for both of you and the kids. You will also get child tax credit of $1,000 each.
You must both declare your worldwide income for 2009. If you have any foreign income, and on that income you paid taxes in the foreign country, then you can claim foreign tax credit (Form 1116) or you can use Foreign Earned Income Exclusion (Form 2555). Your U.S. Tax Return: U.S. Citizen or Resident with Foreign Income

You will complete forms W7 (application for ITIN) for your spouse and children and attach with your tax return. You can also deduct moving expenses. Use form 3903.

Hi,
Ok So what I understood is -

Since I don't pass STP test, I can file as Non-Resident Allien as Married Filing jointly, and in this case I don't need to declare my Worlwide income. Am I right?

Non-resident aliens CANNOT file jointly.

However, non-resident aliens also do NOT report world-wide income, but rather ONLY U.S.-sourced income on the NRA tax return (Form 1040NR or 1040NR-EZ).