I have realised that I need to file a US income tax return.

I left the USA when I was 15 years old & have never filed a US income tax return.

I realised recently that I need to file. My income in Canada (AB) is about 130K.

What should I do? I have read that I can file 1 year, 3 years, 6 years or more.

There is no clear consensus here and I find it kinda confusing.

Has anyone done this ?

Right now I am just planning to file my 2011 return (IRS) and see how it goes.

I would love advise.