Non citizen nor alien that worked in a foreign country most of 2016 but now i'm in the US as a resident, shall i pay taxes in the US for 3 months?

[bravejolie]

During 2016 i worked outside the US and paid taxes there, and during that time i wasn't a US citizen nor i have any type of US visa, i was just a foreign person. 

In October i came to the US with a greencard, so i'm a resident now. I got my W2 from my company, but i've worked in the US only for 3 months.

Do i have to pay taxes in the US too? I thought nobody can pay taxes in two different countries for the same year, what should i do?

[NickS]

Yes you would need to file federal and state taxes for the months you were in the country making money. If you are a U.S. citizen or resident alien, you must report income from all sources within and outside of the U.S. This is true whether or not you receive a Form W-2 Wage and Tax Statement,  a Form 1099 (Information Return) or the foreign equivalents.

[bravejolie]

Thanks for your help. I guess when you say 'report income' it doesn't mean i have to pay taxes for that income right? Because i already pay them in the foreign country. Would i need to proof that i paid taxes from that income with any document from that foreign country?