Tax filing as a green card holder is pretty similar to US citizens. The only caveat is that you will be paying tax on both income earned from inside and outside the US. This includes income from foreign investments, assets and pensions. You are also eligible to apply for a
tax filing extension, just like other taxpayers.
You can avoid being taxed, or can be taxed at a lower rate on foreign income, if you are a dual resident of a country that is part of a
tax treaty with the US. The same goes for if you happen to have “ongoing and indefinite” ties to that country, whether it is in terms of a job, family or a permanent residence. This qualifies you as a “bona fide resident,” and you can claim the
Foreign Earned Income Exclusion tax credit, which allows you to keep any foreign income you earn tax-free.
So if you work full-time in the US, you’ll get a W-2 from your employer that you can use to file your tax return. But if you also work part-time at your Canadian friend’s web development company, you’ll have to report that income on your annual 1040, too.
To do this, you’ll need a
Form 1099 from your friend, which will have the income you earned for the work you did for his company. This means you’ll also be treated as a self-employed individual and will have to pay
self-employment tax. If you think you’ll owe the IRS more than $1,000 in tax in a year, you will have to pay quarterly taxes with
Form 1040-ES. You can use a
tax estimate calculator to find out how much you'll owe.