Oh, I'm not sure, but I assume if you didn't file last year, then you will have to file for 2008 and include the income you earned in the UK from Sept - Dec 2008 on your tax forms. It doesn't sound like you would meet the criteria for foreign earned income exclusion for 2008, though (you need to have lived abroad for a certain number of days before you qualify for that) so not sure how that affects your situation. You should be able to work this out from that info pack on the IRS site, though, I would think, and you can download booklets from previous years, as well, I believe.