If you're wondering how the IRS knows how much you owe since you haven't filed, it's because the IRS has filed a Substitute for Return (SFR) on your behalf. ... With no response, the IRS issues a notice of deficiency. After that, you owe tax, and the agency starts the collection process.
I recommend that you file your complete returns to adjust the tax returns that IRS filed for you.
Please review the following link for the recommended course of action.
https://www.irs.gov/pub/irs-utl/2013_NTF_Dealing_with_SFRs.pdf