I travelled to US in August 2009 and will stay here for 10 months. I am married and my wife has not travelled with me and will not be coming in future as well.

I want to know if I can file tax returns for 2009 as married and claim tax benefits.

Yes, for 2009, you can file joint return as residents. You can file the return only after you complete the Substantial Presence Test in 2010. Then for 2010, you will file dual status tax return. Your U.S. Tax Return: Substantial Presence Test

On the joint return, you must both report your worldwide income for 2009. If you paid taxes in a foreign country, then you can file Form 2555 (Foreign Earned Income Exclusion) or Form 1116 Foreign tax credit.

This means that even though my wife will not be coming to US, I can avail the tax benefits.

What will be the criteria for my substantial presence test as the above doesn't tell anything if I have no presence for previous years.

The Substantial Presence Test (SPT) requires you stay in the U.S. in aggregate, for 183 days.

However, if the days are split over two years, you can only count one-third of the previous year's days to the SPT.

Let's assume you arrived on 15 Aug 09, and stayed 138 days in 2009. You would permitted to count ONLY 46 of those days for SPT purposes.

You would meet SPT on the 137th day of 2010, which would be 17 May 2010.

It means I can not avail the dependent tax benefits of my wife for year 2009 (As I will not able to pass STP for year 2009),

but I can avail dependent tax benefits for the year 2010 provided I will pass SPT (1/3 days of 2009 + rest of the days of 2010 = 183).

No, you can file joint return for 2009, but you must file tax return only after May 17, 2010 (the day when you complete SPT in 2009). You will also attach a statement that you both choose to be treated as residents for 2009.

If you will file resident return for 2009, then you must take care of any other filing requirement by residents. One such form is FBAR.

Thanks for all the answers. It helped a lot.

As for me completing SPT in year 2010 will take around 5 months of the year 2010. And it is a lot of time so one last question

What will be the last date (or deadline) for filing tax returns for the year 2009.

I assume it would be later than May 2010 otherwise I will not be able to complete SPT for 2009.

The stated deadline, with a Form 4828 filed to extension, is 15 Oct 2010.

The actual deadline in 15 April 2013. After that point, any refund due is forfeited due to the statute of limitations.