I used to live in America but moved back to the UK. When I moved back to the UK I didn't fill any paperwork for leaving the USA. I still have my social security number and green card. I know that officially my green card should be void, although it's an older one with no expiry date on it. I wonder what would happen if I simply flew back to the USA, started working again and filed taxes. I've got a bank account over in the USA still, and an address. Or what would happen if I filed a 1040a with NO EARNINGS. I can't send the IRS any P45s because I haven't been there to work. Would I simply fall back into the system nice and easily? I'm wondering this because I really want to go back to USA and work as a teacher. If I've not filled any paperwork to leave USA, do they know I've gone? How would they know if I simply just come back into the country again, start working, file taxes. Any comments? Do you know of anyone who has done this successfully?