What you need is a tax form and W-2. Chances are you will have to fill out 1040EZ. However, because you only earned $5000, you probably will get most of the tax back anyways.Besides, if you already went back to Korea and are not planning to come back, I think it's up to you to pay tax. If the income tax was deducted from your pay, then you already paid tax and you don't have to fill out anything unless you want the money back. If tax was not deducted, then you have to fill out the form if you are planning on paying tax. In that case, you probably will need I-90 instead of W-2 I hope this was of some help.