Changing filing status on US taxes

Since arriving in the UK in June 2006 (tax years 2006 & 2007), I have filed using the Head of Household status made allowable for spouses of non-resident aliens without ITIN. This worked out well so far for us. But because we are planning to move back to the US in 2011, I am thinking about changing to married filing jointly. 1) Right now only DH is working, so we want to make sure that we maintain 3 years of tax records above that 125% of the poverty line necessary for the US visa process. 2) Likewise, I know that one measure of 'how married' you are for the visa is having tax returns filed jointly. I think that to change all I need to do is go to the US Embassy and file for his ITIN. Then we could change to married filing jointly in 2008. Does anyone else have experience with this process?

Apart from needing an ITIN you'd both need to file an election under section 6013(g) with the first return you choose to file jointly.

This would mean including all his worldwide income & gains on your joint US returns - including things that are tax-free here suich as gambling winnings, lottery prizes, ISAs, gain on sale of home, gain on repaying mortgage, employer pension contributions etc; so you'd need to figure out if it would cost you money to make this election.