um, I dont know how it is in the states, but in canada you have to file every year, its illegal not to.
You have to declare all forms of income. If you dont get a slip from your company showing what you made and if you paid taxes.. (T4 for us), you have to declare how much you made (sometimes proved with bank statements) and then pay taxes on what you made. And they usually want their money NOW. You can pay under a payment plan though.
If you dont file or lie, they can nail you for evasion and monetarily penalize you with possible jailtime.