I rented out my house in london UK from May 2007. I want to know when do I have to fill the tax return showing my rental income and pay the tax to the govt. what is the process to pay the tax

Yearly tax time means I need to declare it next year i.e. I don't have to worry this year, can you specify?

You would have to wait for yearly tax time to declare it as rental income.

Are we speaking about U.K. taxes or U.S. taxes?

If U.K. you need to post the question on a forum that deals with U.K. taxes. This forum is for United States taxes.

If U.S. the tax will be due when you file your tax return early in 2008 for tax year 2007.

Is your question "do you claim the foreign rental income earned on your US tax return?" Please clarify.

If the poster is a resident alien in the U.S. he must report ALL income from ALL sources world-wide.