I have a general partnership (Form 1065) that moved effective end of 12/31/11 so the 2011 tax year ended in the old state and 2012 will be in a new state. I presume I should use the new address for filing 2011 tax year 1065 and the state tax return for 2011 (even though new address is out of old state now). But I wonder what IRS address I should mail the return and automatic extension request to? Should I use the one based on the old address in which the partnership ended out the year or use the one on the new address for 2011? I'm thinking it should be based upon the new address but want to make sure. Also, will the old state, California, understand that the new 2012 address was not the address of partnership residency for 2011 or will I need to somehow explain that in the state filings?